Substrate processing method and substrate processing apparatus

ABSTRACT

One of a setting dissolved oxygen concentration and a setting atmosphere oxygen concentration is determined based on a required etching amount. Thereafter, based on the required etching amount and the one of the determined setting dissolved oxygen concentration and setting atmosphere oxygen concentration, the other of the setting dissolved oxygen concentration and the setting atmosphere oxygen concentration is determined. A low oxygen gas whose oxygen concentration is equal or approached to the determined setting atmosphere oxygen concentration flows into a chamber that houses a substrate. Furthermore, an etching liquid whose dissolved oxygen is reduced such that its dissolved oxygen concentration is equal or approached to the determined setting dissolved oxygen concentration is supplied to the entire region of the upper surface of the substrate held horizontally.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 16/232,103, filed on Dec. 26, 2018, which claims the benefit ofpriority to Japanese Patent Application No. 2018-004531, filed on Jan.15, 2018. The entire contents of both of these applications are herebyincorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a substrate processing method and asubstrate processing apparatus that process a substrate. Examples ofsubstrates to be processed include a semiconductor wafer, a substratefor a flat panel display (FPD) such as a liquid crystal display and anorganic electroluminescence (organic EL) display, a substrate for anoptical disc, a substrate for a magnetic disk, a substrate for amagneto-optical disc, a substrate for a photomask, a ceramic substrate,a substrate for a solar cell, and the like.

2. Description of Related Art

In the manufacturing process of a semiconductor device, a liquid crystaldisplay, etc., a substrate processing apparatus is used which processesa substrate such as a semiconductor wafer or a glass substrate for aliquid crystal display. JP 2015-153947 A discloses a single substrateprocessing-type substrate processing apparatus which supplies asubstrate with a processing liquid having a low dissolved oxygenconcentration in a state where an oxygen concentration in an atmosphereis low.

SUMMARY OF THE INVENTION

Conventionally, as disclosed in JP 2015-153947 A, it is considered thatit is preferable to minimize the dissolved oxygen concentration of theprocessing liquid and the oxygen concentration in the atmosphere.However, according to the study and research conducted by the presentinventors, it was found that when a processing liquid is used to etch asubstrate, not only the dissolved oxygen concentration of the processingliquid and an oxygen concentration in an atmosphere, but also adifference therebetween could affect the etching results.

For example, it is found that when the oxygen concentration in theatmosphere is excessively low with respect to the dissolved oxygenconcentration of the processing liquid, the uniformity of the etchingmay be degraded. Hence, it is not necessarily preferable that thedissolved oxygen concentration of the processing liquid and the oxygenconcentration in the atmosphere be low. It is also found that thedistribution of the amount of etching over the entire region of thefront surface or the rear surface of the substrate can be changed bycontrolling not only the dissolved oxygen concentration of theprocessing liquid and the oxygen concentration in the atmosphere butalso a difference therebetween.

Hence, an object of the present invention is to provide a substrateprocessing method and a substrate processing apparatus which can etch amain surface of a substrate while controlling a distribution of anamount of etching by supplying an entire main surface of the substratewith an etching liquid having a low dissolved oxygen concentration in astate where an oxygen concentration in an atmosphere is low.

A preferred embodiment of the present invention provides a substrateprocessing method which includes a first oxygen concentrationdetermination step of determining one of a setting dissolved oxygenconcentration which indicates a setting value of a dissolved oxygenconcentration of an etching liquid and a setting atmosphere oxygenconcentration which indicates a setting value of an oxygen concentrationin an atmosphere in contact with the etching liquid held on a mainsurface of a substrate, based on a required etching amount whichindicates a required value of an amount of etching of the main surfaceof the substrate, a second oxygen concentration determination step ofdetermining the other of the setting dissolved oxygen concentration andthe setting atmosphere oxygen concentration based on the requiredetching amount and the one of the setting dissolved oxygen concentrationand the setting atmosphere oxygen concentration determined in the firstoxygen concentration determination step, a low oxygen gas supply step ofcausing a low oxygen gas, whose oxygen concentration is lower than anoxygen concentration of air and equal or approached to the settingatmosphere oxygen concentration determined in the first oxygenconcentration determination step or the second oxygen concentrationdetermination step, to flow into a chamber that houses the substrate,and an etching step of etching the main surface of the substrate bysupplying an entire region of the main surface of the substrate heldhorizontally with the etching liquid whose dissolved oxygen is reducedsuch that the dissolved oxygen concentration of the etching liquid isequal or approached to the setting dissolved oxygen concentrationdetermined in the first oxygen concentration determination step or thesecond oxygen concentration determination step, while causing the lowoxygen gas that has flowed into the chamber in the low oxygen gas supplystep to be in contact with the etching liquid held on the main surfaceof the substrate.

In this method, the etching liquid having a low dissolved oxygenconcentration is supplied to the main surface of the substrate in astate where the oxygen concentration in the atmosphere is lowered. Thus,it is possible to supply the etching liquid to the entire region of themain surface of the substrate while controlling the amount of oxygendissolved into the etching liquid held on the substrate. The actualdissolved oxygen concentration of the etching liquid supplied to themain surface of the substrate is equal or approached to the settingdissolved oxygen concentration. Similarly, the actual oxygenconcentration in the atmosphere in contact with the etching liquid heldon the main surface of the substrate is equal or approached to thesetting atmosphere oxygen concentration.

The setting dissolved oxygen concentration and the setting atmosphereoxygen concentration are not set independently based on the requiredetching amount but are related to each other. Specifically, one of thesetting dissolved oxygen concentration and the setting atmosphere oxygenconcentration is determined based on the required etching amount. Then,based on the determined value (one of the setting dissolved oxygenconcentration and the setting atmosphere oxygen concentration) and therequired etching amount, the other of the setting dissolved oxygenconcentration and the setting atmosphere oxygen concentration isdetermined. In other words, not only the setting dissolved oxygenconcentration and the setting atmosphere oxygen concentration but alsothe difference between the setting dissolved oxygen concentration andthe setting atmosphere oxygen concentration is controlled.

As described above, the setting dissolved oxygen concentration and thesetting atmosphere oxygen concentration are lowered while controllingthe difference between the setting dissolved oxygen concentration andthe setting atmosphere oxygen concentration, and thus it is possible tochange the distribution of the amount of etching over the main surfaceof the substrate without changing a landing position of the etchingliquid with respect to the main surface of the substrate. For example,it is possible to uniformly etch the entire region of the main surfaceof the substrate with a constant amount of etching, and to etch the mainsurface of the substrate such that the distribution of the amount ofetching is formed in the shape of a cone or an inverted cone. Hence, itis possible to etch the main surface of the substrate while controllingthe distribution of the amount of etching.

The main surface of the substrate means either the front surface (deviceformation surface) or the rear surface (non-device formation surface) ofthe substrate. When the substrate is held horizontally, the uppersurface or the lower surface of the substrate corresponds to the mainsurface. The main surface of the substrate may be any of the frontsurface and the rear surface of the substrate. The low oxygen gas meansa gas which has an oxygen concentration lower than the oxygenconcentration (about 21 vol %) of the air.

In the preferred embodiment, at least one of the following features maybe added to the substrate processing method.

One of the first oxygen concentration determination step and the secondoxygen concentration determination step includes either a step ofdetermining, as the setting dissolved oxygen concentration, a valuelarger than a minimum value in a range of values which can be set as thesetting dissolved oxygen concentration or a step of determining, as thesetting atmosphere oxygen concentration, a value larger than a minimumvalue in a range of values which can be set as the setting atmosphereoxygen concentration.

In this method, a value which is larger than the minimum value in therange of values that can be set as the setting dissolved oxygenconcentration or the setting atmosphere oxygen concentration is set asthe setting dissolved oxygen concentration or the setting atmosphereoxygen concentration. In other words, unlike the conventional method inwhich the setting dissolved oxygen concentration and the settingatmosphere oxygen concentration are set to values as small as possible,the setting dissolved oxygen concentration, the setting atmosphereoxygen concentration and the difference therebetween are controlled.Thus, it is possible to etch the main surface of the substrate while thedistribution of the amount of etching is being controlled.

The etching step includes a liquid discharge step of causing a liquiddischarge port to discharge the etching liquid, whose dissolved oxygenis reduced such that the dissolved oxygen concentration of the etchingliquid is equal or approached to the setting dissolved oxygenconcentration determined in the first oxygen concentration determinationstep or the second oxygen concentration determination step, toward themain surface of the substrate held horizontally, while locating alanding position of the etching liquid, where the etching liquiddischarged from the liquid discharge port first contacts the mainsurface of the substrate, in a central portion of the main surface ofthe substrate after start of the discharge of the etching liquid untilstop of the discharge of the etching liquid.

In this method, the landing position of the etching liquid is positionedin the central portion of the main surface of the substrate after thestart of the discharge until the stop of the discharge. In such a caseas well, the difference between the setting dissolved oxygenconcentration and the setting atmosphere oxygen concentration iscontrolled, and thus it is possible to control the distribution of theamount of etching. Hence, it is not necessary to move the landingposition of the etching liquid with respect to the main surface of thesubstrate or to provide a plurality of liquid discharge ports whichdischarge the etching liquid toward the main surface of the substrate inorder to control the distribution of the amount of etching.

The second oxygen concentration determination step is a step ofdetermining, based on the required etching amount and the one of thesetting dissolved oxygen concentration and the setting atmosphere oxygenconcentration determined in the first oxygen concentration determinationstep, the other of the setting dissolved oxygen concentration and thesetting atmosphere oxygen concentration such that the distribution ofthe amount of etching over the main surface of the substrate is formedin the shape of a cone or an inverted cone.

In this method, the setting dissolved oxygen concentration and thesetting atmosphere oxygen concentration are set such that thedistribution of the amount of etching over the main surface of thesubstrate is formed in the shape of a cone or an inverted cone. When themain surface of the substrate before the etching is in the shape of acone, the main surface of the substrate is etched such that thedistribution of the amount of etching over the main surface of thesubstrate is formed in the shape of a cone, and thus it is possible toimprove the flatness of the main surface of the substrate after theetching. Similarly, when the main surface of the substrate before theetching is in the shape of an inverted cone, the main surface of thesubstrate is etched such that the distribution of the amount of etchingover the main surface of the substrate is formed in the shape of aninverted cone, and thus it is possible to improve the flatness of themain surface of the substrate after the etching.

The first oxygen concentration determination step is a step ofdetermining the setting dissolved oxygen concentration based on therequired etching amount, and the second oxygen concentrationdetermination step is a step of determining the setting atmosphereoxygen concentration based on the required etching amount and thesetting dissolved oxygen concentration determined in the first oxygenconcentration determination step.

In this method, after the setting dissolved oxygen concentration isdetermined, the setting atmosphere oxygen concentration is determined.The etching rate in the landing position depends on the dissolved oxygenconcentration of the etching liquid. In other words, the settingatmosphere oxygen concentration does not significantly affect theetching rate in the landing position. Instead, the gradient of theetching rate, that is, the gradient of a straight line which connectsthe etching rate in the landing position and the etching rate in anarbitrary position within the main surface of the substrate depends onthe dissolved oxygen concentration of the etching liquid and the oxygenconcentration in the atmosphere. Hence, when the setting dissolvedoxygen concentration is previously determined, the etching rate in thelanding position and the gradient of the etching rate can be setrelatively easily.

By contrast, when the setting atmosphere oxygen concentration ispreviously determined, the conditions other than the setting dissolvedoxygen concentration and the setting atmosphere oxygen concentration mayneed to be changed. For example, when the setting atmosphere oxygenconcentration is previously determined, in order to obtain the intendedgradient of the etching rate, the setting dissolved oxygen concentrationis significantly restricted. When the intended etching rate cannot beobtained by the determined setting dissolved oxygen concentration,another condition such as the time of supply of the etching liquid mayneed to be changed. Hence, the setting dissolved oxygen concentration ispreviously determined, and thus the etching rate in the landing positionand the gradient of the etching rate can be set relatively easily.

The low oxygen gas supply step includes a step of causing the low oxygengas to flow from an opening provided in an opposed surface of an opposedmember to a space between the main surface of the substrate and theopposed surface of the opposed member, while causing the opposed surfaceof the opposed member which is movable within the chamber to face themain surface of the substrate.

In this method, the low oxygen gas which has an oxygen concentrationlower than the oxygen concentration of the air flows out from theopening provided in the opposed surface of the opposed member and flowsinto the space between the main surface of the substrate and the opposedsurface of the opposed member. Thus, the space between the substrate andthe opposed member is filled with the low oxygen gas, and thus theoxygen concentration in the atmosphere is lowered. Hence, as comparedwith a case where the oxygen concentration is lowered in the entireinternal space of the chamber, the used amount of low oxygen gas can bereduced, and thus it is possible to change the oxygen concentration in ashort period of time.

The opposed member may be a shielding member which is movable verticallyin the chamber and which is arranged above the substrate or may be aspin base which is rotatable around a vertical rotation axis within thechamber and which is arranged below the substrate.

The low oxygen gas supply step includes a step of causing the low oxygengas to flow from a central opening, which is provided in the opposedsurface of the opposed member and faces a central portion of the mainsurface of the substrate, to the space between the main surface of thesubstrate and the opposed surface of the opposed member and a step ofcausing the low oxygen gas to flow from an outer opening, which isprovided in the opposed surface of the opposed member and faces aportion of the main surface of the substrate other than the centralportion of the main surface of the substrate, to the space between themain surface of the substrate and the opposed surface of the opposedmember.

In this method, the central opening and the outer opening are providedin the opposed surface of the opposed member. The central opening facesthe central portion of the main surface of the substrate. The outeropening is arranged outside the central opening. The low oxygen gasflowing out from the central opening flows outward in the space betweenthe substrate and the opposed member. Similarly, the low oxygen gasflowing out from the outer opening flows outward in the space betweenthe substrate and the opposed member. Hence, as compared with a casewhere the outer opening is not provided, another gas is unlikely to flowin the space between the substrate and the opposed member. Thus, it ispossible to more accurately control the oxygen concentration in thespace between the substrate and the opposed member.

The low oxygen gas supply step includes a step of causing the low oxygengas to flow from an upper end portion of the chamber into the chamber,while causing a gas within the chamber to flow out from a lower endportion of the chamber.

In this method, the low oxygen gas flows from the upper end portion ofthe chamber into the chamber. The low oxygen gas that has flowed intothe chamber flows toward the lower end portion of the chamber and isdischarged from the lower end portion of the chamber to the outside ofthe chamber. Thus, the interior of the chamber is filled with the lowoxygen gas, and thus the oxygen concentration in the atmosphere islowered. Hence, the oxygen concentration in the atmosphere can belowered without provision of members such as the shielding memberarranged above the substrate. Thus, it is possible to downsize thechamber.

The substrate processing method includes a first dissolved oxygenconcentration adjustment step of lowering the dissolved oxygenconcentration of the etching liquid within a first tank to a firstdissolved oxygen concentration by reducing the dissolved oxygen in theetching liquid, and a second dissolved oxygen concentration adjustmentstep of lowering the dissolved oxygen concentration of the etchingliquid within a second tank to a second dissolved oxygen concentrationdifferent from the first dissolved oxygen concentration by reducing thedissolved oxygen in the etching liquid, and the etching step includes aselection step of selecting, among the first tank and the second tank, atank that stores the etching liquid having the dissolved oxygenconcentration closer to the setting dissolved oxygen concentrationdetermined in the first oxygen concentration determination step or thesecond oxygen concentration determination step and a liquid dischargestep of discharging the etching liquid within the tank selected in theselection step toward the main surface of the substrate heldhorizontally.

In this method, the etching liquids having different dissolved oxygenconcentrations are stored in the first tank and the second tank. Thedetermined setting dissolved oxygen concentration is compared with afirst dissolved oxygen concentration which indicates the dissolvedoxygen concentration of the etching liquid within the first tank and asecond dissolved oxygen concentration which indicates the dissolvedoxygen concentration of the etching liquid within the second tank. Whenthe first dissolved oxygen concentration is equal or close to thedetermined setting dissolved oxygen concentration, the etching liquidwithin the first tank is supplied to the main surface of the substrate.On the other hand, when the second dissolved oxygen concentration isequal or close to the determined setting dissolved oxygen concentration,the etching liquid within the second tank is supplied to the mainsurface of the substrate.

It is difficult to change immediately the dissolved oxygen concentrationof the etching liquid. Hence, when the dissolved oxygen concentration ofthe etching liquid within the same tank is changed, a certain amount oftime is needed. By contrast, when the etching liquids having differentdissolved oxygen concentrations are previously stored in the first tankand the second tank, the dissolved oxygen concentration of the etchingliquid to be supplied to the main surface of the substrate can bechanged immediately. Thus, it is possible to reduce the downtime (timeduring which the substrate processing cannot be executed) of thesubstrate processing apparatus, and thus it is possible to reduce theamount of decrease in the throughput (the number of substrates processedper unit time) of the substrate processing apparatus.

The etching step is a step of etching a polysilicon film formed on themain surface of the substrate by supplying the entire region of the mainsurface of the substrate held horizontally with the etching liquid whosedissolved oxygen is reduced such that the dissolved oxygen concentrationof the etching liquid is equal or approached to the setting dissolvedoxygen concentration determined in the first oxygen concentrationdetermination step or the second oxygen concentration determination stepwhile causing the low oxygen gas that has flowed into the chamber in thelow oxygen gas supply step to be in contact with the etching liquid heldon the main surface of the substrate.

In this method, the etching liquid having a low dissolved oxygenconcentration is supplied to the main surface of the substrate on whichthe polysilicon film is exposed in the state where the oxygenconcentration in the atmosphere is lowered. Thus, it is possible to etchthe polysilicon film formed on the main surface of the substrate whilecontrolling the amount of oxygen dissolved into the etching liquid heldon the substrate. The polysilicon film is an example of a thin filmwhich is affected by the dissolved oxygen concentration of the etchingliquid. Hence, not only the setting dissolved oxygen concentration andthe setting atmosphere oxygen concentration but also the differencetherebetween is controlled, and thus it is possible to etch thepolysilicon film while controlling the distribution of the amount ofetching.

Another preferred embodiment of the present invention provides asubstrate processing apparatus including a substrate holding unit whichholds a substrate horizontally, an etching liquid supply unit whichsupplies a main surface of the substrate held by the substrate holdingunit with an etching liquid whose dissolved oxygen is reduced, a chamberwhich houses the substrate held by the substrate holding unit, a lowoxygen gas supply unit which causes a low oxygen gas having an oxygenconcentration lower than an oxygen concentration of air to flow into thechamber housing the substrate so as to adjust an oxygen concentration inan atmosphere in contact with the etching liquid held on the mainsurface of the substrate, a dissolved oxygen concentration change unitwhich changes a dissolved oxygen concentration of the etching liquid tobe supplied to the substrate from the etching liquid supply unit, anatmosphere oxygen concentration change unit which changes the oxygenconcentration in the atmosphere to be adjusted by the low oxygen gassupply unit, and a controller.

The controller executes a first oxygen concentration determination stepof determining one of a setting dissolved oxygen concentration whichindicates a setting value of the dissolved oxygen concentration of theetching liquid and a setting atmosphere oxygen concentration whichindicates a setting value of the oxygen concentration in the atmospherein contact with the etching liquid held on the main surface of thesubstrate, based on a required etching amount which indicates a requiredvalue of an amount of etching of the main surface of the substrate, asecond oxygen concentration determination step of determining the otherof the setting dissolved oxygen concentration and the setting atmosphereoxygen concentration based on the required etching amount and the one ofthe setting dissolved oxygen concentration and the setting atmosphereoxygen concentration determined in the first oxygen concentrationdetermination step, a low oxygen gas supply step of causing the lowoxygen gas, whose oxygen concentration is lower than an oxygenconcentration of air and equal or approached to the setting atmosphereoxygen concentration determined in the first oxygen concentrationdetermination step or the second oxygen concentration determinationstep, to flow into the chamber that houses the substrate, and an etchingstep of etching the main surface of the substrate by supplying an entireregion of the main surface of the substrate held horizontally with theetching liquid whose dissolved oxygen is reduced such that the dissolvedoxygen concentration of the etching liquid is equal or approached to thesetting dissolved oxygen concentration determined in the first oxygenconcentration determination step or the second oxygen concentrationdetermination step, while causing the low oxygen gas that has flowedinto the chamber in the low oxygen gas supply step to be in contact withthe etching liquid held on the main surface of the substrate. Accordingto this arrangement, the same effects as the effects described aboveregarding the substrate processing method can be obtained.

In the preferred embodiment, at least one of the following features maybe added to the substrate processing apparatus.

One of the first oxygen concentration determination step and the secondoxygen concentration determination step includes either a step ofdetermining, as the setting dissolved oxygen concentration, a valuelarger than a minimum value in a range of values which can be set as thesetting dissolved oxygen concentration or a step of determining, as thesetting atmosphere oxygen concentration, a value larger than a minimumvalue in a range of values which can be set as the setting atmosphereoxygen concentration. According to this arrangement, the same effects asthe effects described above regarding the substrate processing methodcan be obtained.

The etching liquid supply unit includes a liquid discharge port whichdischarges the etching liquid toward the main surface of the substrateheld by the substrate holding unit, and the etching step includes aliquid discharge step of causing the liquid discharge port to dischargethe etching liquid, whose dissolved oxygen is reduced such that thedissolved oxygen concentration of the etching liquid is equal orapproached to the setting dissolved oxygen concentration determined inthe first oxygen concentration determination step or the second oxygenconcentration determination step, toward the main surface of thesubstrate held horizontally, while locating a landing position of theetching liquid, where the etching liquid discharged from the liquiddischarge port first contacts the main surface of the substrate, in acentral portion of the main surface of the substrate after start of thedischarge of the etching liquid until stop of the discharge of theetching liquid. According to this arrangement, the same effects as theeffects described above regarding the substrate processing method can beobtained.

The second oxygen concentration determination step is a step ofdetermining, based on the required etching amount and the one of thesetting dissolved oxygen concentration and the setting atmosphere oxygenconcentration determined in the first oxygen concentration determinationstep, the other of the setting dissolved oxygen concentration and thesetting atmosphere oxygen concentration such that the distribution ofthe amount of etching over the main surface of the substrate is formedin the shape of a cone or an inverted cone. According to thisarrangement, the same effects as the effects described above regardingthe substrate processing method can be obtained.

The first oxygen concentration determination step is a step ofdetermining the setting dissolved oxygen concentration based on therequired etching amount, and the second oxygen concentrationdetermination step is a step of determining the setting atmosphereoxygen concentration based on the required etching amount and thesetting dissolved oxygen concentration determined in the first oxygenconcentration determination step. According to this arrangement, thesame effects as the effects described above regarding the substrateprocessing method can be obtained.

The substrate processing apparatus further includes an opposed memberwhich includes an opposed member which is movable within the chamber andwhich includes an opposed surface that faces the main surface of thesubstrate held by the substrate holding unit and an opening provided inthe opposed surface, and the low oxygen gas supply step includes a stepof causing the low oxygen gas to flow from the opening provided in theopposed surface to a space between the main surface of the substrate andthe opposed surface of the opposed member, while causing the opposedsurface of the opposed member which is movable within the chamber toface the main surface of the substrate. According to this arrangement,the same effects as the effects described above regarding the substrateprocessing method can be obtained.

The opening of the opposed member includes a central opening that isprovided in the opposed surface of the opposed member and faces acentral portion of the main surface of the substrate and an outeropening that is provided in the opposed surface of the opposed memberand faces a portion of the main surface of the substrate other than thecentral portion of the main surface of the substrate, and the low oxygengas supply step includes a step of causing the low oxygen gas to flowfrom the central opening to the space between the main surface of thesubstrate and the opposed surface of the opposed member and a step ofcausing the low oxygen gas to flow from the outer opening to the spacebetween the main surface of the substrate and the opposed surface of theopposed member. According to this arrangement, the same effects as theeffects described above regarding the substrate processing method can beobtained.

The low oxygen gas supply unit includes a fan unit which causes the lowoxygen gas to flow from an upper end portion of the chamber into thechamber and an exhaust duct which causes a gas within the chamber toflow out from a lower end portion of the chamber, and the low oxygen gassupply step includes a step of causing the low oxygen gas to flow fromthe upper end portion of the chamber into the chamber while causing thegas within the chamber to flow out from the lower end portion of thechamber. According to this arrangement, the same effects as the effectsdescribed above regarding the substrate processing method can beobtained.

The etching liquid supply unit includes a first tank which stores theetching liquid, a second tank which stores the etching liquid, a firstdissolved oxygen concentration change unit which lowers the dissolvedoxygen concentration of the etching liquid within the first tank and asecond dissolved oxygen concentration change unit which lowers thedissolved oxygen concentration of the etching liquid within the secondtank, the controller further executes a first dissolved oxygenconcentration adjustment step of lowering the dissolved oxygenconcentration of the etching liquid within the first tank to the firstdissolved oxygen concentration by reducing the dissolved oxygen in theetching liquid and a second dissolved oxygen concentration adjustmentstep of lowering the dissolved oxygen concentration of the etchingliquid within a second tank to the second dissolved oxygen concentrationdifferent from the first dissolved oxygen concentration by reducing thedissolved oxygen in the etching liquid and the etching step includes aselection step of selecting, among the first tank and the second tank, atank that stores the etching liquid having the dissolved oxygenconcentration closer to the setting dissolved oxygen concentrationdetermined in the first oxygen concentration determination step or thesecond oxygen concentration determination step and a liquid dischargestep of discharging the etching liquid within the tank selected in theselection step toward the main surface of the substrate heldhorizontally. According to this arrangement, the same effects as theeffects described above regarding the substrate processing method can beobtained.

The etching step is a step of etching a polysilicon film formed on themain surface of the substrate by supplying the entire region of the mainsurface held horizontally with the etching liquid whose dissolved oxygenis reduced such that the dissolved oxygen concentration of the etchingliquid is equal or approached to the setting dissolved oxygenconcentration determined in the first oxygen concentration determinationstep or the second oxygen concentration determination step while causingthe low oxygen gas that has flowed into the chamber in the low oxygengas supply step to be in contact with the etching liquid held on themain surface of the substrate. According to this arrangement, the sameeffects as the effects described above regarding the substrateprocessing method can be obtained.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a substrate processing apparatus accordingto a first preferred embodiment of the present invention viewed fromabove.

FIG. 2 is a schematic view of the interior of a processing unit includedin the substrate processing apparatus when the interior is viewedhorizontally.

FIG. 3 is a partially enlarged view of FIG. 2.

FIG. 4 is a schematic view showing a chemical liquid producing unitwhich produces a chemical liquid to be supplied to a substrate and adissolved oxygen concentration change unit which adjusts the dissolvedoxygen concentration of the chemical liquid.

FIG. 5 is a block diagram showing the hardware of a controller.

FIG. 6 is a process chart for describing an example of the processing ofthe substrate which is executed by the substrate processing apparatus.

FIGS. 7A to 7D are conceptual diagrams showing the distribution of anetching rate when an etching liquid is supplied to the upper surface ofthe substrate on which a polysilicon film is exposed so as to etch thepolysilicon film.

FIG. 8 is a block diagram showing the functional blocks of thecontroller.

FIG. 9 is a schematic view showing a vertical cross section of ashielding member according to a second preferred embodiment of thepresent invention.

FIG. 10 is a schematic view showing the bottom surface of the shieldingmember according to the second preferred embodiment of the presentinvention.

FIG. 11 is a schematic view of the interior of a processing unitaccording to a third preferred embodiment of the present invention whenthe interior is viewed horizontally.

FIG. 12 is a schematic view of the interior of the processing unitaccording to the third preferred embodiment of the present inventionwhen the interior is viewed from above.

FIG. 13 is a schematic view showing chemical liquid producing units anddissolved oxygen concentration change units according to a fourthpreferred embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a schematic view of a substrate processing apparatus 1according to a first preferred embodiment of the present inventionviewed from above.

The substrate processing apparatus 1 is a single substrateprocessing-type apparatus which processes disc-shaped substrates W suchas a semiconductor wafer one by one. The substrate processing apparatus1 includes load ports LP which hold carriers C that house one or moresubstrates W constituting one lot, a plurality of processing units 2which process the substrates W transferred from the carriers C on theload ports LP with a processing fluid such as a processing liquid or aprocessing gas, transfer robots which transfer the substrates W betweenthe carriers C on the load ports LP and the processing units 2 and acontroller 3 which controls the substrate processing apparatus 1.

The transfer robots include an indexer robot IR which carries thesubstrates W into and out from the carriers C on the load ports LP and acenter robot CR which carries the substrates W into and out from theprocessing units 2. The indexer robot IR transfers the substrates Wbetween the load ports LP and the center robot CR, the center robot CRtransfers the substrates W between the indexer robot IR and theprocessing units 2. The center robot CR and the indexer robot IR includehands H1 and H2 which support the substrates W, respectively.

FIG. 2 is a schematic view of the interior of the processing unit 2included in the substrate processing apparatus 1 when the interior isviewed horizontally. FIG. 3 is a partially enlarged view of FIG. 2. FIG.2 shows a state where a raising/lowering frame 32 and a shielding member33 are positioned in a lower position, and FIG. 3 shows a state wherethe raising/lowering frame 32 and the shielding member 33 are positionedin an upper position.

The processing unit 2 includes a box-shaped chamber 4 which has aninternal space, a spin chuck 10 which rotates one substrate W around avertical rotation axis A1 passing through the central portion of thesubstrate W while holding the substrate W horizontally within thechamber 4 and a tubular processing cup 23 which surrounds the spin chuck10 around the rotation axis A1.

The chamber 4 includes a box-shaped partition wall 6 provided with acarry-in/carry-out port 6 b through which the substrate W passes, and ashutter 7 which opens and closes the carry-in/carry-out port 6 b. Thechamber 4 further includes a rectifying plate 8 which is arranged belowan air outlet 6 a that is open in the ceiling surface of the partitionwall 6. An FFU 5 (fan filter unit) which feeds clean air (air filteredby a filter) is arranged on the air outlet 6 a. An exhaust duct 9 whichdischarges a gas within the chamber 4 is connected to the processing cup23. The air outlet 6 a is provided in an upper end portion of thechamber 4, and the exhaust duct 9 is arranged in a lower end portion ofthe chamber 4. A portion of the exhaust duct 9 is arranged outside thechamber 4.

The rectifying plate 8 partitions the internal space of the partitionwall 6 into an upper space Su above the rectifying plate 8 and a lowerspace SL below the rectifying plate 8. The upper space Su between theceiling surface of the partition wall 6 and the upper surface of therectifying plate 8 is a diffusion space in which the clean air diffuses.The lower space SL between the lower surface of the rectifying plate 8and the floor surface of the partition wall 6 is a processing space inwhich the substrate W is processed. The spin chuck 10 and the processingcup 23 are arranged in the lower space SL. A distance in a verticaldirection from the floor surface of the partition wall 6 to the lowersurface of the rectifying plate 8 is longer than a distance in thevertical direction from the upper surface of the rectifying plate 8 tothe ceiling surface of the partition wall 6.

The FFU 5 feeds the clean air via the air outlet 6 a to the upper spaceSu. The clean air supplied to the upper space Su hits the rectifyingplate 8 and diffuses in the upper space Su. The clean air within theupper space Su passes through a plurality of through holes whichvertically penetrate the rectifying plate 8, and flows downward from theentire region of the rectifying plate 8. The clean air supplied to thelower space SL is sucked into the processing cup 23 and is dischargedthrough the exhaust duct 9 from the lower end portion of the chamber 4.Thus, a uniform downward flow (down flow) of the clean air which flowsdownward from the rectifying plate 8 is formed in the lower space SL.The processing of the substrate W is performed in a state where thedownward flow of the clean air is formed.

The spin chuck 10 includes a disc-shaped spin base 12 which is held by ahorizontal posture, a plurality of chuck pins 11 which hold thesubstrate W in the horizontal posture above the spin base 12, a spinshaft 13 which extends downward from the central portion of the spinbase 12 and a spin motor 14 which rotates the spin shaft 13 so as torotate the spin base 12 and the chuck pins 11. The spin chuck 10 is notlimited to a clamping type chuck which brings the chuck pins 11 intocontact with the outer circumferential surface of the substrate W, andthe spin chuck 10 may be a vacuum-type chuck which sucks the rearsurface (lower surface) of the substrate W that is a non-deviceformation surface to the upper surface 12 u of the spin base 12 so as tohold the substrate W horizontally.

The spin base 12 includes the upper surface 12 u which is arranged belowthe substrate W. The upper surface 12 u of the spin base 12 is parallelto the lower surface of the substrate W. The upper surface 12 u of thespin base 12 is an opposed surface which faces the lower surface of thesubstrate W. The upper surface 12 u of the spin base 12 has a circularring shaped configuration which surrounds the rotation axis A1. Theoutside diameter of the upper surface 12 u of the spin base 12 is largerthan that of the substrate W. The chuck pins 11 protrude upward from theouter circumferential portion of the upper surface 12 u of the spin base12. The chuck pins 11 are held on the spin base 12. The substrate W isheld on the chuck pins 11 in a state where the lower surface of thesubstrate W is separated from the upper surface 12 u of the spin base12.

The processing unit 2 includes a lower surface nozzle 15 whichdischarges the processing liquid toward the central portion of the lowersurface of the substrate W. The lower surface nozzle 15 includes anozzle disc portion which is arranged between the upper surface 12 u ofthe spin base 12 and the lower surface of the substrate W and a nozzletubular portion which extends downward from the nozzle disc portion. Theliquid discharge port 15 p of the lower surface nozzle 15 is open in thecentral portion of the upper surface of the nozzle disc portion. In astate where the substrate W is held on the spin chuck 10, the liquiddischarge port 15 p of the lower surface nozzle 15 faces the centralportion of the lower surface of the substrate W.

The substrate processing apparatus 1 includes a lower rinse liquidpiping 16 which guides a rinse liquid to the lower surface nozzle 15 anda lower rinse liquid valve 17 which is interposed in the lower rinseliquid piping 16. When the lower rinse liquid valve 17 is opened, therinse liquid guided by the lower rinse liquid piping 16 is dischargedupward from the lower surface nozzle 15 and supplied to the centralportion of the lower surface of the substrate W. The rinse liquidsupplied to the lower surface nozzle 15 is pure water (DIW: deionizedwater). The rinse liquid supplied to the lower surface nozzle 15 is notlimited to pure water, and may be any one of IPA (isopropyl alcohol),carbonated water, electrolytic ion water, hydrogen water, ozone waterand a hydrochloric acid water of a dilute concentration (for example,about 1 to 100 ppm).

Although not shown, the lower rinse liquid valve 17 includes a valvebody provided with an internal flow path where the liquid flows and anannular valve seat surrounding the internal flow path, a valve memberwhich is movable with respect to the valve seat and an actuator whichmoves the valve member between a closed position where the valve membercontacts the valve seat and an opened position where the valve member isseparated from the valve seat. The same applies to other valves. Theactuator may be a pneumatic actuator or an electric actuator or anactuator other than those. The controller 3 controls the actuator so asto open and close the lower rinse liquid valve 17.

The outer circumferential surface of the lower surface nozzle 15 and theinner circumferential surface of the spin base 12 defines a lowertubular path 19 which extends vertically. The lower tubular path 19includes a lower central opening 18 which is open in the central portionof the upper surface 12 u of the spin base 12. The lower central opening18 is arranged below the nozzle disc portion of the lower surface nozzle15. The substrate processing apparatus 1 includes a lower gas piping 20which guides an inert gas supplied via the lower tubular path 19 to thelower central opening 18, a lower gas valve 21 which is interposed inthe lower gas piping 20 and a lower gas flow rate adjusting valve 22which changes the flow rate of the inert gas supplied from the lower gaspiping 20 to the lower tubular path 19.

The inert gas supplied from the lower gas piping 20 to the lower tubularpath 19 is nitrogen gas. The inert gas is not limited to nitrogen gas,and may be another inert gas such as helium gas or argon gas. Theseinert gases are low oxygen gases which have an oxygen concentrationlower than an oxygen concentration (about 21 vol %) in air.

When the lower gas valve 21 is opened, the nitrogen gas supplied fromthe lower gas piping 20 to the lower tubular path 19 is dischargedupward from the lower central opening 18 at a flow rate corresponding tothe degree of opening of the lower gas flow rate adjusting valve 22.Thereafter, the nitrogen gas flows radially in all directions betweenthe lower surface of the substrate W and the upper surface 12 u of thespin base 12. Thus, the space between the substrate W and the spin base12 is filled with the nitrogen gas, and thus an oxygen concentration inan atmosphere is reduced. The oxygen concentration in the space betweenthe substrate W and the spin base 12 is changed according to the degreeof opening of the lower gas valve 21 and the lower gas flow rateadjusting valve 22.

The processing cup 23 includes a plurality of guards 25 which receivethe liquid discharged outward from the substrate W, a plurality of cups26 which receive the liquid guided downward by the guards 25 and acylindrical outer wall member 24 which surrounds the guards 25 and thecups 26. FIG. 2 shows an example where two guards 25 and two cups 26 areprovided.

The guard 25 includes a cylindrical guard tubular portion 25 b whichsurrounds the spin chuck 10 and an annular guard ceiling portion 25 awhich extends obliquely upward from the upper end portion of the guardtubular portion 25 b toward the rotation axis A1. Guard ceiling portions25 a vertically overlap each other, and guard tubular portions 25 b arearranged concentrically. The cups 26 are arranged below the guardtubular portions 25 b, respectively. The cup 26 defines an annularliquid receiving groove which is open upward.

The processing unit 2 includes a guard raising/lowering unit 27 whichindividually raises and lowers the guards 25. The guard raising/loweringunit 27 locates the guard 25 in an arbitrary position from an upperposition to a lower position. The upper position is the position inwhich the upper end 25 u of the guard 25 is arranged higher than aholding position in which the substrate W held by the spin chuck 10 isarranged. The lower position is the position in which the upper end 25 uof the guard 25 is arranged lower than the holding position. The annularupper end of the guard ceiling portion 25 a corresponds to the upper end25 u of the guard 25. The upper end 25 u of the guard 25 surrounds thesubstrate W and the spin base 12 in plan view.

When the processing liquid is supplied to the substrate W in a statewhere the spin chuck 10 rotates the substrate W, the processing liquidsupplied to the substrate W is spun off around the substrate W. When theprocessing liquid is supplied to the substrate W, at least one of theupper ends 25 u of the guards 25 is arranged higher than the substrateW. Hence, the processing liquid such as the chemical liquid or the rinseliquid which is discharged around the substrate W is received by any oneof the guards 25 and guided to the cup 26 corresponding to this guard25.

As shown in FIG. 3, the processing unit 2 includes the raising/loweringframe 32 which is arranged above the spin chuck 10, the shielding member33 which is suspended from the raising/lowering frame 32, a centernozzle 45 which is inserted into the shielding member 33 and a shieldingmember raising/lowering unit 31 which raises and lowers theraising/lowering frame 32 so as to raise and lower the shielding member33 and the center nozzle 45. The raising/lowering frame 32, theshielding member 33 and the center nozzle 45 are arranged below therectifying plate 8.

The shielding member 33 includes a disc portion 36 which is arrangedabove the spin chuck 10 and a tubular portion 37 which extends downwardfrom the outer circumferential portion of the disc portion 36. Theshielding member 33 includes an inner surface which has a cup-shapedconfiguration that is concave upward. The inner surface of the shieldingmember 33 includes a lower surface 36L of the disc portion 36 and theinner circumferential surface 37 i of the tubular portion 37. In thefollowing description, the lower surface 36L of the disc portion 36 mayalso be referred to as the lower surface 36L of the shielding member 33.

The lower surface 36L of the disc portion 36 is an opposed surface whichfaces the upper surface of the substrate W. The lower surface 36L of thedisc portion 36 is parallel to the upper surface of the substrate W. Theinner circumferential surface 37 i of the tubular portion 37 extendsdownward from the outer circumferential edge of the lower surface 36L ofthe lower surface 36L. The inside diameter of the tubular portion 37 isincreased as the lower end of the inner circumferential surface 37 i isapproached. The inside diameter of the lower end of the innercircumferential surface 37 i of the tubular portion 37 is larger thanthe diameter of the substrate W. The inside diameter of the lower end ofthe inner circumferential surface 37 i of the tubular portion 37 may belarger than the outside diameter of the spin base 12. When the shieldingmember 33 is arranged in the lower position (position shown in FIG. 2)which will be described below, the substrate W is surrounded by theinner circumferential surface 37 i of the tubular portion 37.

The lower surface 36L of the disc portion 36 has a circular ring shapedconfiguration which surrounds the rotation axis A1. The innercircumferential edge of the lower surface 36L of the disc portion 36defines an upper central opening 38 which is open in the central portionof the lower surface 36L of the disc portion 36. The innercircumferential surface of the shielding member 33 defines a throughhole which extends upward from the upper central opening 38. The throughhole of the shielding member 33 vertically penetrates the shieldingmember 33. The center nozzle 45 is inserted into the through hole of theshielding member 33. The outside diameter of the lower end of the centernozzle 45 is smaller than the diameter of the upper central opening 38.

The inner circumferential surface of the shielding member 33 is coaxialwith the outer circumferential surface of the center nozzle 45. Theinner circumferential surface of the shielding member 33 surrounds theouter circumferential surface of the center nozzle 45 across an intervalin a radial direction (direction orthogonal to the rotation axis A1).The inner circumferential surface of the shielding member 33 and theouter circumferential surface of the center nozzle 45 define an uppertubular path 39 which extends vertically. The center nozzle 45 protrudesupward from the raising/lowering frame 32 and the shielding member 33.When the shielding member 33 is suspended from the raising/loweringframe 32, the lower end of the center nozzle 45 is arranged higher thanthe lower surface 36L of the disc portion 36. The processing liquid suchas the chemical liquid or the rinse liquid is discharged downward fromthe lower end of the center nozzle 45.

The shielding member 33 includes a tubular connection portion 35 whichextends upward from the disc portion 36, and an annular flange portion34 which extends outward from the upper end portion of the connectionportion 35. The flange portion 34 is arranged higher than the discportion 36 and the tubular portion 37 of the shielding member 33. Theflange portion 34 is parallel to the disc portion 36. The outsidediameter of the flange portion 34 is smaller than that of the tubularportion 37. The flange portion 34 is supported on the lower plate 32L ofthe raising/lowering frame 32 which will be described below.

The raising/lowering frame 32 includes an upper plate 32 u which ispositioned higher than the flange portion 34 of the shielding member 33,a side ring 32 s which extends downward from the upper plate 32 u andsurrounds the flange portion 34, and an annular lower plate 32L whichextends inward from the lower end portion of the side ring 32 s and islocated below the flange portion 34 of the shielding member 33. Theouter circumferential portion of the flange portion 34 is arrangedbetween the upper plate 32 u and the lower plate 32L. The outercircumferential portion of the flange portion 34 is movable verticallyin a space between the upper plate 32 u and the lower plate 32L.

The raising/lowering frame 32 and the shielding member 33 includelocating protrusions 41 and locating holes 42 which restrict therelative movement of the raising/lowering frame 32 and the shieldingmember 33 in a circumferential direction (direction around the rotationaxis A1) in a state where the shielding member 33 is supported by theraising/lowering frame 32. FIG. 2 shows an example where a plurality oflocating protrusions 41 are provided on the lower plate 32L and where aplurality of locating holes 42 are provided in the flange portion 34.The locating protrusions 41 may be provided on the flange portion 34,and the locating holes 42 may be provided in the lower plate 32L.

The locating protrusions 41 are arranged on a circle which has a centerarranged on the rotation axis A1. Similarly, the locating holes 42 arearranged on a circle which has a center arranged on the rotation axisA1. The locating holes 42 are arranged in the circumferential directionwith the same regularity as the locating protrusions 41. The locatingprotrusions 41 which protrude upward from the upper surface of the lowerplate 32L are inserted into the locating holes 42 which extend upwardfrom the lower surface of the flange portion 34. Thus, the movement ofthe shielding member 33 in the circumferential direction with respect tothe raising/lowering frame 32 is restricted.

The shielding member 33 includes a plurality of upper support portions43 which protrude downward from the inner surface of the shieldingmember 33. The spin chuck 10 includes a plurality of lower supportportions 44 which supports the upper support portions 43, respectively.The upper support portions 43 are surrounded by the tubular portion 37of the shielding member 33. The lower ends of the upper support portions43 are arranged higher than the lower end of the tubular portion 37. Thedistance in the radial direction from the rotation axis A1 to the uppersupport portion 43 is larger than the radius of the substrate W.Similarly, the distance in the radial direction from the rotation axisA1 to the lower support portion 44 is larger than the radius of thesubstrate W. The lower support portions 44 protrude upward from theupper surface 12 u of the spin base 12. The lower support portions 44are arranged on the outer side with respect to the chuck pins 11.

The upper support portions 43 are arranged on a circle which has acenter arranged on the rotation axis A1. Similarly, the lower supportportions 44 are arranged on a circle which has a center arranged on therotation axis A1. The lower support portions 44 are arranged in thecircumferential direction with the same regularity as the upper supportportions 43. The lower support portions 44 are rotated together with thespin base 12 around the rotation axis A1. The rotational angle of thespin base 12 is changed by the spin motor 14. When the spin base 12 isarranged at a reference rotational angle, the upper support portions 43respectively overlap the lower support portions 44 in plan view.

The shielding member raising/lowering unit 31 is coupled to theraising/lowering frame 32. When the shielding member raising/loweringunit 31 lowers the raising/lowering frame 32 in a state where the flangeportion 34 of the shielding member 33 is supported on the lower plate32L of the raising/lowering frame 32, the shielding member 33 is alsolowered. When the shielding member raising/lowering unit 31 lowers theshielding member 33 in a state where the spin base 12 is arranged atsuch a reference rotational angle that the upper support portions 43respectively overlap the lower support portions 44 in plan view, thelower end portions of the upper support portions contact the upper endportions of the lower support portions 44. Thus, the upper supportportions 43 are respectively supported on the lower support portions 44.

When the shielding member raising/lowering unit 31 lowers theraising/lowering frame 32 after the upper support portions 43 of theshielding member 33 contact the lower support portions 44 of the spinchuck 10, the lower plate 32L of the raising/lowering frame 32 is moveddownward with respect to the flange portion 34 of the shielding member33. Thus, the lower plate 32L is separated from the flange portion 34,and thus the locating protrusions 41 are removed from the locating holes42. Furthermore, the raising/lowering frame 32 and the center nozzle 45are moved downward with respect to the shielding member 33, and thus thedifference in height between the lower end of the center nozzle 45 andthe lower surface 36L of the disc portion 36 of the shielding member 33is reduced. Here, the raising/lowering frame 32 is arranged at such aheight (the lower position which will be described below) that theflange portion 34 of the shielding member 33 does not contact the upperplate 32 u of the raising/lowering frame 32.

The shielding member raising/lowering unit 31 locates theraising/lowering frame 32 in an arbitrary position from the upperposition (position shown in FIG. 3) to the lower position (positionshown in FIG. 2). The upper position is the position in which thelocating protrusions 41 are inserted into the locating holes 42 and inwhich the flange portion 34 of the shielding member 33 contact the lowerplate 32L of the raising/lowering frame 32. In other words, the upperposition is the position in which the shielding member 33 is suspendedfrom the raising/lowering frame 32. The lower position is the positionin which the lower plate 32L is separated from the flange portion 34 andin which the locating protrusions 41 are removed from the locating holes42. In other words, the lower position is the position in which thecoupling of the raising/lowering frame 32 and the shielding member 33 isreleased and in which the shielding member 33 does not contact anyportion of the raising/lowering frame 32.

When the raising/lowering frame 32 and the shielding member 33 are movedto the lower position, the lower ends of the tubular portion 37 of theshielding member 33 are arranged lower than the lower surface of thesubstrate W, and thus the space between the upper surface of thesubstrate W and the lower surface 36L of the shielding member 33 issurrounded by the tubular portion 37 of the shielding member 33. Hence,the space between the upper surface of the substrate W and the lowersurface 36L of the shielding member 33 is shielded not only from anatmosphere above the shielding member 33 but also from an atmospherearound the shielding member 33. Thus, it is possible to enhance thesealing performance to seal the space between the upper surface of thesubstrate W and the lower surface 36L of the shielding member 33.

Furthermore, when the raising/lowering frame 32 and the shielding member33 are arranged in the lower position, even if the shielding member 33is rotated around the rotation axis A1, the shielding member 33 isprevented from colliding with the raising/lowering frame 32. When theupper support portions 43 of the shielding member 33 are supported onthe lower support portions 44 of the spin chuck 10, the upper supportportions 43 and the lower support portions 44 engage with each other,and thus the relative movement of the upper support portions 43 and thelower support portions 44 in the circumferential direction is prevented.When the spin motor 14 rotates in this state, the torque of the spinmotor 14 is transmitted to the shielding member 33 via the upper supportportions 43 and the lower support portions 44. Thus, the shieldingmember 33 rotates in the same direction and at the same speed as thespin base 12 in a state where the raising/lowering frame 32 and thecenter nozzle 45 are stationary.

The center nozzle 45 includes a plurality of liquid discharge portsthrough which the liquid is discharged and a gas discharge port throughwhich the gas is discharged. The liquid discharge ports include a firstchemical liquid discharge port 46 through which a first chemical liquidis discharged, a second chemical liquid discharge port 47 through whicha second chemical liquid is discharged and an upper rinse liquiddischarge port 48 through which the rinse liquid is discharged. The gasdischarge port is an upper gas discharge port 49 through which an inertgas is discharged. The first chemical liquid discharge port 46, thesecond chemical liquid discharge port 47, the upper rinse liquiddischarge port 48 are open in the lower end of the center nozzle 45. Theupper gas discharge port 49 is open in the outer circumferential surfaceof the center nozzle 45.

Each of the first chemical liquid and the second chemical liquid is aliquid which contains at least one of sulfuric acid, nitric acid,hydrochloric acid, hydrofluoric acid, phosphoric acid, acetic acid,ammonia water, hydrogen peroxide water, organic acids (for example,citric acid, oxalic acid), organic alkalis (for example, TMAH:tetramethylammonium hydroxide), inorganic alkalis (for example, NaOH:sodium hydroxide), a surfactant and a corrosion inhibitor, for example.Sulfuric acid, nitric acid, hydrochloric acid, hydrofluoric acid,phosphoric acid, acetic acid, ammonia water, hydrogen peroxide water,citric acid, oxalic acid, inorganic alkalis and TMAH are etchingliquids.

The first chemical liquid and the second chemical liquid may be the sametypes of chemical liquid or may be different types of chemical liquids.FIG. 2, etc., show an example where the first chemical liquid is DHF(dilute hydrofluoric acid) and where the second chemical liquid is TMAH.Also, FIG. 2, etc., show the example where the rinse liquid supplied tothe center nozzle 45 is pure water and where the inert gas supplied tothe center nozzle 45 is nitrogen gas. The rinse liquid supplied to thecenter nozzle 45 may be a rinse liquid other than pure water. The inertgas supplied to the center nozzle 45 may be an inert gas other thannitrogen gas.

The substrate processing apparatus 1 includes a first chemical liquidpiping 50 which guides the first chemical liquid to the center nozzle45, a first chemical liquid valve 51 which is interposed in the firstchemical liquid piping 50, a second chemical liquid piping 52 whichguides the second chemical liquid to the center nozzle 45, a secondchemical liquid valve 53 which is interposed in the second chemicalliquid piping 52, an upper rinse liquid piping 54 which guides the rinseliquid to the center nozzle 45 and an upper rinse liquid valve 55 whichis interposed in the upper rinse liquid piping 54. The substrateprocessing apparatus 1 further includes an upper gas piping 56 whichguides the gas to the center nozzle 45, an upper gas valve 57 which isinterposed in the upper gas piping 56 and an upper gas flow rateadjusting valve 58 which changes the flow rate of the gas supplied fromthe upper gas piping 56 to the center nozzle 45.

When the first chemical liquid valve 51 is opened, the first chemicalliquid is supplied to the center nozzle 45 and is discharged downwardfrom the first chemical liquid discharge port 46 which is open in thelower end of the center nozzle 45. The substrate processing apparatus 1includes a chemical liquid producing unit 61 which produces the secondchemical liquid. When the second chemical liquid valve 53 is opened, thesecond chemical liquid produced in the chemical liquid producing unit 61is supplied to the center nozzle 45 and is discharged downward from thesecond chemical liquid discharge port 47 which is open in the lower endof the center nozzle 45. When the upper rinse liquid valve 55 is opened,the rinse liquid is supplied to the center nozzle 45 and is dischargeddownward from the upper rinse liquid discharge port 48 which is open inthe lower end of the center nozzle 45. Thus, the chemical liquid or therinse liquid is supplied to the upper surface of the substrate W.

When the upper gas valve 57 is opened, the nitrogen gas guided by theupper gas piping 56 is supplied to the center nozzle 45 at a flow ratecorresponding to the degree of opening of the upper gas flow rateadjusting valve 58 and is discharged obliquely downward from the uppergas discharge port 49 which is open in the outer circumferential surfaceof the center nozzle 45. Thereafter, the nitrogen gas flows downwardwithin the upper tubular path 39 while flowing in the circumferentialdirection within the upper tubular path 39. The nitrogen gas that hasreached the lower end of the upper tubular path 39 flows downward fromthe lower end of the upper tubular path 39. Thereafter, the nitrogen gasflows radially in all directions in the space between the upper surfaceof the substrate W and the lower surface 36L of the shielding member 33.Thus, the space between the substrate Wand the shielding member 33 isfilled with the nitrogen gas, and the oxygen concentration in theatmosphere is reduced. The oxygen concentration in the space between thesubstrate W and the shielding member 33 is changed according to thedegree of opening of the upper gas valve 57 and the upper gas flow rateadjusting valve 58.

FIG. 4 is a schematic view showing the chemical liquid producing unit 61which produces the chemical liquid to be supplied to the substrate W anda dissolved oxygen concentration change unit 67 which adjusts thedissolved oxygen concentration of the chemical liquid.

The chemical liquid producing unit 61 includes a tank 62 in which thechemical liquid supplied to the substrate W is stored and a circulationpiping 63 which defines an annular circulation path that circulates thechemical liquid within the tank 62. The chemical liquid producing unit61 further includes a pump 64 which feeds the chemical liquid within thetank 62 to the circulation piping 63 and a filter 66 which removesforeign matter such as particles from the chemical liquid flowing thoughthe circulation path. In addition thereto, the chemical liquid producingunit 61 may include a temperature adjuster 65 which changes thetemperature of the chemical liquid within the tank 62 by heating orcooling the chemical liquid.

The upstream end and the downstream end of the circulation piping 63 areconnected to the tank 62. The upstream end of the second chemical liquidpiping 52 is connected to the circulation piping 63 and the downstreamend of the second chemical liquid piping 52 is connected to the centernozzle 45. The pump 64, the temperature adjuster 65 and the filter 66are interposed in the circulation piping 63. The temperature adjuster 65may be a heater which heats the liquid at a temperature higher than theroom temperature (for example, 20 to 30° C.), may be a cooler whichcools the liquid at a temperature lower than the room temperature or mayhave both functions of heating and cooling.

The pump 64 constantly feeds the chemical liquid within the tank 62 intothe circulation piping 63. The chemical liquid is fed from the tank 62to the upstream end of the circulation piping 63 and is returned fromthe downstream end of the circulation piping 63 to the tank 62. Thus,the chemical liquid within the tank 62 is circulated along thecirculation path. While the chemical liquid is being circulated alongthe circulation path, the temperature of the chemical liquid is adjustedby the temperature adjuster 65. Thus, the chemical liquid within thetank 62 is maintained at a constant temperature. When the secondchemical liquid valve 53 is opened, some of the chemical liquid flowingwithin the circulation piping 63 is supplied via the second chemicalliquid piping 52 to the center nozzle 45.

The substrate processing apparatus 1 includes the dissolved oxygenconcentration change unit 67 which adjusts the dissolved oxygenconcentration of the chemical liquid. The dissolved oxygen concentrationchange unit 67 includes a gas supply piping 68 which supplies the gasinto the tank 62 so as to dissolve the gas into the chemical liquidwithin the tank 62. The dissolved oxygen concentration change unit 67further includes an inert gas piping 69 which supplies the inert gas tothe gas supply piping 68, an inert gas valve 70 which is opened andclosed between an opened state where the inert gas flows from the inertgas piping 69 to the gas supply piping 68 and a closed state where theinert gas is stopped at the inert gas piping 69 and an inert gas flowrate adjusting valve 71 which changes the flow rate of the inert gassupplied from the inert gas piping 69 to the gas supply piping 68.

The gas supply piping 68 is a bubbling piping which includes gasdischarge ports 68 p which are arranged in the chemical liquid withinthe tank 62. When the inert gas valve 70 is opened, that is, when theinert gas valve 70 is switched from the closed state to the openedstate, the inert gas such as nitrogen gas is discharged from the gasdischarge ports 68 p at a flow rate corresponding to the degree ofopening of the inert gas flow rate adjusting valve 71. Thus, a largenumber of air bubbles are formed in the chemical liquid within the tank62, and thus the inert gas is dissolved in the chemical liquid withinthe tank 62. Here, the dissolved oxygen is discharged from the chemicalliquid, and thus the dissolved oxygen concentration of the chemicalliquid is lowered. The dissolved oxygen concentration of the chemicalliquid within the tank 62 is changed by changing the flow rate of thenitrogen gas discharged from the gas discharge ports 68 p.

The dissolved oxygen concentration change unit 67 may include, inaddition to the inert gas piping 69, etc., an oxygen containing gaspiping 72 which supplies an oxygen containing gas containing oxygen suchas clean air to the gas supply piping 68, an oxygen containing gas valve73 which is opened and closed between an opened state where the oxygencontaining gas flows from the oxygen containing gas piping 72 to the gassupply piping 68 and a closed state where the oxygen containing gas isstopped at the oxygen containing gas piping 72 and an oxygen containinggas flow rate adjusting valve 74 which changes the flow rate of theoxygen containing gas supplied from the oxygen containing gas piping 72to the gas supply piping 68.

When the oxygen containing gas valve 73 is opened, air which is anexample of the oxygen containing gas is discharged from the gasdischarge ports 68 p at a flow rate corresponding to the degree ofopening of the oxygen containing gas flow rate adjusting valve 74. Thus,a large number of air bubbles are formed in the chemical liquid withinthe tank 62, and thus the air is dissolved in the chemical liquid withinthe tank 62. Air contains oxygen at about 21% of the volume, whereas thenitrogen does not contain oxygen or contains only a very small amount ofoxygen. Hence, as compared with a case where the air is not suppliedinto the tank 62, it is possible to increase the dissolved oxygenconcentration of the chemical liquid within the tank 62 in a shortperiod of time. For example, when the dissolved oxygen concentration ofthe chemical liquid is excessively lowered with respect to a settingvalue, the air may be intentionally dissolved into the chemical liquidwithin the tank 62.

The dissolved oxygen concentration change unit 67 may further include anoxygen meter 75 which measures the dissolved oxygen concentration of thechemical liquid. FIG. 4 shows an example where the oxygen meter 75 isinterposed in a measurement piping 76. The oxygen meter 75 may beinterposed in the circulation piping 63. The upstream end of themeasurement piping 76 is connected to the filter 66, and the downstreamend of the measurement piping 76 is connected to the tank 62. Theupstream end of the measurement piping 76 may be connected to thecirculation piping 63. Some of the chemical liquid within thecirculation piping 63 flows into the measurement piping 76 and isreturned to the tank 62. The oxygen meter 75 measures the dissolvedoxygen concentration of the chemical liquid which flows into themeasurement piping 76. The degree of opening of at least one of theinert gas valve 70, the inert gas flow rate adjusting valve 71, theoxygen containing gas valve 73 and the oxygen containing gas flow rateadjusting valve 74 is changed according to the measurement value of theoxygen meter 75.

FIG. 5 is a block diagram showing the hardware of the controller 3.

The controller 3 is a computer which includes a computer main body 81and a peripheral device 84 which is connected to the computer main body81. The computer main body 81 includes a CPU 82 (central processingunit) which executes various types of commands and a main storage device83 which stores information. The peripheral device 84 includes anauxiliary storage device 85 which stores information such as a programP, a reading device 86 which reads information from a removable medium Mand a communication device 87 which communicates with other devices suchas a host computer.

The controller 3 is connected to an input device 88 and a display 89.The input device 88 is operated when an operator such as a user or amaintenance operator inputs information to the substrate processingapparatus 1. The information is displayed on the screen of the display89. The input device 88 may be any one of a keyboard, a pointing deviceand a touch panel or may be a device other than those. A touch paneldisplay which serves both as the input device 88 and the display 89 maybe provided in the substrate processing apparatus 1.

The CPU 82 executes the program P stored in the auxiliary storage device85. The program P within the auxiliary storage device 85 may bepreviously installed in the controller 3, may be fed through the readingdevice 86 from the removable medium M to the auxiliary storage device 85or may be fed from an external device such as the host computer to theauxiliary storage device 85 through the communication device 87.

The auxiliary storage device 85 and the removable medium M arenonvolatile memories which retain memory even without power beingsupplied. The auxiliary storage device 85 is, for example, a magneticstorage device such as a hard disk drive. The removable medium M is, forexample, an optical disc such as a compact disc or a semiconductormemory such as a memory card. The removable medium M is an example of acomputer readable recording medium in which the program P is recorded.

The auxiliary storage device 85 stores a plurality of recipes. Theauxiliary storage device 85 further stores dissolved oxygenconcentration determination data and atmosphere oxygen concentrationdetermination data which will be described below. The recipe isinformation which specifies the details of processing, processingconditions and processing procedures of the substrate W. A plurality ofrecipes differ from each other in at least one of the details ofprocessing, the processing conditions and the processing procedures ofthe substrate W. The controller 3 controls the substrate processingapparatus 1 such that the substrate W is processed according to therecipe designated by the host computer. The controller 3 executesindividual steps described below by controlling the substrate processingapparatus 1. In other words, the controller 3 is programmed to executethe individual steps described below.

FIG. 6 is a process chart for describing an example of the processing ofthe substrate W which is executed by the substrate processing apparatus1. In the following description, FIGS. 1, 2, 3 and 6 are referenced.

A specific example of the processing of the substrate W is etchingprocessing in which TMAH as an example of an etching liquid is suppliedto the front surface of the substrate W (silicon wafer) on which apolysilicon film is exposed so as to etch the polysilicon film. A targetto be etched may be a thin film other than the polysilicon film or thesubstrate W itself (silicon wafer). Processing other than the etchingmay be executed.

When the substrate W is processed by the substrate processing apparatus1, a carry-in step of carrying the substrate W into the chamber 4 isperformed (step S1 in FIG. 6).

Specifically, in a state where the raising/lowering frame 32 and theshielding member 33 are positioned in the upper position and where allthe guards 25 are positioned in the lower position, the center robot CRcauses the hand H1 to enter the chamber 4 while supporting the substrateW with the hand H1. Then, the center robot CR places, on the chuck pins11, the substrate W on the hand H1 with the front surface of thesubstrate W directed upward. Thereafter, the chuck pins 11 are pressedonto the outer circumferential surface of the substrate W, and thus thesubstrate W is grasped. The center robot CR places the substrate W onthe spin chuck 10 and thereafter retracts the hand H1 from the interiorof the chamber 4.

Then, the upper gas valve 57 and the lower gas valve 21 are opened, andthus the upper central opening 38 of the shielding member 33 and thelower central opening 18 of the spin base 12 start the discharge of thenitrogen gas. Thus, the oxygen concentration in the atmosphere incontact with the substrate W is reduced. Furthermore, the shieldingmember raising/lowering unit 31 lowers the raising/lowering frame 32from the upper position to the lower position, and the guardraising/lowering unit 27 raises any one of the guards 25 from the lowerposition to the upper position. Here, the spin base 12 is held at such areference rotational angle where the upper support portions 43respectively overlap the lower support portions 44 in plan view. Hence,the upper support portions 43 of the shielding member 33 are supportedon the lower support portions 44 of the spin base 12, and the shieldingmember 33 is separated from the raising/lowering frame 32. Thereafter,the spin motor 14 is driven so as to start the rotation of the substrateW (step S2 in FIG. 6).

Then, a first chemical liquid supply step of supplying DHF as an exampleof the first chemical liquid to the upper surface of the substrate W isperformed (step S3 in FIG. 6).

Specifically, in a state where the shielding member 33 is positioned inthe lower position, the first chemical liquid valve 51 is opened, andthus the center nozzle 45 starts the discharge of the DHF. The DHFdischarged from the center nozzle 45 lands on the central portion of theupper surface of the substrate W and thereafter flows outward along theupper surface of the substrate W which is being rotated. Thus, a liquidfilm of the DHF which covers the entire region of the upper surface ofthe substrate W is formed, and the DHF is supplied to the entire regionof the upper surface of the substrate W. When a predetermined timeelapses after the opening of the first chemical liquid valve 51, thefirst chemical liquid valve 51 is closed, and the discharge of the DHFis stopped.

Then, a first rinse liquid supply step of supplying pure water as anexample of the rinse liquid to the upper surface of the substrate W isperformed (step S4 in FIG. 6).

Specifically, in a state where the shielding member 33 is positioned inthe lower position, the upper rinse liquid valve 55 is opened, and thusthe center nozzle 45 starts the discharge of the pure water. The purewater which lands on the central portion of the upper surface of thesubstrate W flows outward along the upper surface of the substrate Wthat is being rotated. The DHF on the substrate W is rinsed off by thepure water discharged from the center nozzle 45. Thus, a liquid film ofthe pure water which covers the entire region of the upper surface ofthe substrate W is formed. When a predetermined time elapses after theopening of the upper rinse liquid valve 55, the upper rinse liquid valve55 is closed, and the discharge of the pure water is stopped.

Then, a second chemical liquid supply step of supplying TMAH as anexample of the second chemical liquid to the upper surface of thesubstrate W is performed (step S5 in FIG. 6).

Specifically, in a state where the shielding member 33 is positioned inthe lower position, the second chemical liquid valve 53 is opened, andthus the center nozzle 45 starts the discharge of the TMAH. Before thestart of the discharge of the TMAH, in order to switch the guards 25which receive the liquid discharged from the substrate W, the guardraising/lowering unit 27 may vertically move at least one of the guards25. The TMAH which lands on the central portion of the upper surface ofthe substrate W flows outward along the upper surface of the substrate Wthat is being rotated. The pure water on the substrate W is replaced bythe TMAH discharged from the center nozzle 45. Thus, a liquid film ofthe TMAH which covers the entire region of the upper surface of thesubstrate W is formed. When a predetermined time elapses after theopening of the second chemical liquid valve 53, the second chemicalliquid valve 53 is closed, and the discharge of the TMAH is stopped.

As described previously, the TMAH is the etching liquid which has a lowdissolved oxygen concentration. The TMAH is supplied to the uppersurface of the substrate W in a state where the oxygen concentration inthe atmosphere is lowered. Hence, the TMAH flows outward along the uppersurface of the substrate W while being in contact with the atmosphere inwhich the oxygen concentration is low. As will be described below, thesetting value of the dissolved oxygen concentration of the TMAH suppliedto the upper surface of the substrate W and the setting value of theoxygen concentration in the atmosphere in contact with the TMAH arerelated to each other in order to control the distribution of the amountof etching.

Then, a second rinse liquid supply step of supplying pure water as anexample of the rinse liquid to the upper surface of the substrate W isperformed (step S6 in FIG. 6).

Specifically, in the state where the shielding member 33 is positionedin the lower position, the upper rinse liquid valve 55 is opened, andthus the center nozzle 45 starts the discharge of the pure water. Thepure water which lands on the central portion of the upper surface ofthe substrate W flows outward along the upper surface of the substrate Wthat is being rotated. The TMAH on the substrate W is rinsed off by thepure water discharged from the center nozzle 45. Thus, a liquid film ofthe pure water which covers the entire region of the upper surface ofthe substrate W is formed. When a predetermined time elapses after theopening of the upper rinse liquid valve 55, the upper rinse liquid valve55 is closed, and the discharge of the pure water is stopped.

Then, a drying step of drying the substrate W by the rotation of thesubstrate W is performed (step S7 in FIG. 6).

Specifically, in the state where the shielding member 33 is positionedin the lower position, the spin motor 14 accelerates the substrate W inthe rotation direction so as to rotate the substrate W at a highrotational speed (for example, several thousands of rpm) higher than therotational speed of the substrate W in a period from the first chemicalliquid supply step to the second rinse liquid supply step. Thus, theliquid is removed from the substrate W, and thus the substrate W isdried. When a predetermined time elapses after the start of thehigh-speed rotation of the substrate W, the spin motor 14 stops therotation. Here, the spin motor 14 stops the spin base 12 at thereference rotational angle. Thus, the rotation of the substrate W isstopped (step S8 in FIG. 6).

Then, a carry-out step of carrying the substrate W out from the chamber4 is performed (step S9 in FIG. 6).

Specifically, the shielding member raising/lowering unit 31 raises theraising/lowering frame 32 to the upper position, and the guardraising/lowering unit 27 lowers all the guards 25 to the lower position.Furthermore, the upper gas valve 57 and the lower gas valve 21 areclosed, and thus the upper central opening 38 of the shielding member 33and the lower central opening 18 of the spin base 12 stop the dischargeof the nitrogen gas. Thereafter, the center robot CR causes the hand H1to enter the chamber 4. After the chuck pins 11 release the grasping ofthe substrate W, the center robot CR supports the substrate W on thespin chuck 10 with the hand H1. Thereafter, the center robot CR retractsthe hand H1 from the interior of the chamber 4 while supporting thesubstrate W with the hand H1. Thus, the processed substrate W is carriedout from the chamber 4.

FIGS. 7A, 7B, 7C and 7D are conceptual diagrams showing the distributionof an etching rate when the etching liquid is supplied to the uppersurface of the substrate W on which the polysilicon film is exposed soas to etch the polysilicon film in a case where the etching liquid is anorganic alkali such as the TMAH.

FIGS. 7A to 7D show the distribution of the etching rate (the amount ofetching per unit time) in the upper surface of the substrate Won astraight line which passes through the center of the upper surface ofthe substrate W and two points positioned on the outer circumferentialedge of the upper surface of the substrate W. The etching ratecorresponds to an etching speed. In the following description, areference line (vertical axis shown in FIGS. 7A to 7D) means a straightline which passes through the center of the upper surface of thesubstrate W and which is orthogonal to the upper surface of thesubstrate W.

In the wet etching of the polysilicon film using an organic alkali suchas the TMAH as an example of the etching liquid, the dissolved oxygen ofthe etching liquid tends to prevent the etching of the polysilicon film.Hence, as the dissolved oxygen concentration of the etching liquidincreases, the etching rate is lowered, whereas as the dissolved oxygenconcentration of the etching liquid is lowered, the etching rateincreases.

When the etching liquid is supplied to the substrate W in a state wherethe dissolved oxygen concentration of the etching liquid is low and theoxygen concentration in the atmosphere is high, the oxygen in theatmosphere is dissolved in the etching liquid flowing outward along theupper surface of the substrate W, and thus the dissolved oxygenconcentration of the etching liquid increases as the outer circumferenceof the substrate W is approached. In other words, the dissolved oxygenconcentration of the etching liquid in the outer circumferential portionof the upper surface of the substrate W is higher than the dissolvedoxygen concentration of the etching liquid in the central portion of theupper surface of the substrate W. Hence, as shown in FIG. 7A, theetching rate shows the distribution of an inverted V-shape substantiallysymmetrical with respect to the reference line. In this case, thesubstrate W is etched such that the distribution of the amount ofetching over the upper surface of the substrate W is formed in the shapeof a cone.

As shown in FIG. 7B, when the etching liquid is supplied to thesubstrate W in a state where only the oxygen concentration in theatmosphere is lowered and conditions, such as the dissolved oxygenconcentration of the etching liquid, other than the oxygen concentrationin the atmosphere are not changed, the amount of oxygen dissolved in theetching liquid on the substrate W is reduced and thus an increase in thedissolved oxygen concentration of the etching liquid on the substrate Wis reduced. Hence, as shown in FIG. 7B, although the etching rate in thecentral portion of the upper surface of the substrate W is hardlychanged, the etching rate in the outer circumferential portion of theupper surface of the substrate W is increased as compared with theetching rate before the oxygen concentration in the atmosphere islowered. Hence, a difference between the etching rate in the centralportion of the upper surface of the substrate W and the etching rate inthe outer circumferential portion of the upper surface of the substrateW is reduced, and thus the uniformity of the etching is enhanced.

FIG. 7C shows the distribution of the etching rate when the dissolvedoxygen concentration of the etching liquid is increased with respect toprocessing conditions in which the distribution of the etching rateshown in FIG. 7B is obtained. The etching rate shown in FIG. 7C draws agentle curve of an inverted V-shape. When the dissolved oxygenconcentration of the etching liquid is increased, the etching rate inthe central portion of the upper surface of the substrate W is lowered.Furthermore, since the oxygen concentration in the atmosphere islowered, the dissolved oxygen concentration of the etching liquid on thesubstrate W is hardly increased. Hence, as shown in FIG. 7C, thedistribution of the etching rate draws a substantially flat curve, andthus the uniformity of the etching is further enhanced. It is consideredthat the same results are obtained when, instead of increasing thedissolved oxygen concentration of the etching liquid, the oxygenconcentration in the atmosphere is further lowered.

FIG. 7D shows the distribution of the etching rate when the dissolvedoxygen concentration of the etching liquid is increased with respect toprocessing conditions in which the distribution of the etching rateshown in FIG. 7C is obtained. When the dissolved oxygen concentration ofthe etching liquid is increased, the etching rate in the central portionof the upper surface of the substrate W is lowered. On the other hand,since the oxygen concentration in the atmosphere is significantlylowered with respect to the dissolved oxygen concentration of theetching liquid, oxygen in the atmosphere is not dissolved in the etchingliquid but nitrogen in the atmosphere is dissolved into the etchingliquid on the substrate W, with the result that the dissolved oxygenconcentration of the etching liquid is lowered. Hence, as shown in FIG.7D, the distribution of the etching rate draws a V-shaped curvesubstantially symmetrical with respect to the reference line. In thiscase, the substrate W is etched such that the distribution of the amountof etching over the upper surface of the substrate W is formed in theshape of an inverted cone.

As described above, when the uniformity of the etching is enhanced, itis not necessarily preferable to minimize the oxygen concentration inthe atmosphere but the oxygen concentration in the atmosphere needs tobe set according to the dissolved oxygen concentration of the etchingliquid supplied to the substrate W. Similarly, when the oxygenconcentration in the atmosphere is constant, if the dissolved oxygenconcentration of the etching liquid is excessively low or high, theuniformity of the etching is lowered. From a different viewpoint, thedistribution of the etching rate over the entire region of the uppersurface of the substrate W can be formed to be flat or can be formed inthe shape of a cone or an inverted cone by relating the dissolved oxygenconcentration of the etching liquid and the oxygen concentration in theatmosphere to each other.

Although in the above description, the case where the etching rate islowered as the dissolved oxygen concentration of the etching liquidincreases is described, the same tendency would apply to a case wherethe etching rate is reduced as the dissolved oxygen concentration of theetching liquid increases. Hence, it is not necessarily preferable tominimize both the dissolved oxygen concentration of the etching liquidand the oxygen concentration in the atmosphere, and in order to controlthe cross-sectional shape (profile) of the upper surface of thesubstrate W after the etching, it is important to control the differencebetween the dissolved oxygen concentration of the etching liquid and theoxygen concentration in the atmosphere.

When the upper surface of the substrate W before the etching is flat,the upper surface of the substrate W is etched such that thedistribution of the etching rate is flat, and thus the upper surface ofthe substrate W after the etching is formed to be flat. When the uppersurface of the substrate W before the etching is formed in the shape ofa cone, the upper surface of the substrate W is etched such that thedistribution of the amount of etching over the upper surface of thesubstrate W is formed in the shape of a cone, and thus it is possible toimprove the flatness of the upper surface of the substrate W after theetching. Similarly, when the upper surface of the substrate W before theetching is formed in the shape of an inverted cone, the upper surface ofthe substrate W is etched such that the distribution of the amount ofetching over the upper surface of the substrate W is formed in the shapeof an inverted cone, and thus it is possible to improve the flatness ofthe upper surface of the substrate W after the etching.

The difference between the amount of etching in the central portion ofthe upper surface of the substrate W and the amount of etching in theouter circumferential portion of the upper surface of the substrate Wdepends not only on the dissolved oxygen concentration of the etchingliquid and the oxygen concentration in the atmosphere but also on aplurality of conditions including the time of supply of the etchingliquid, the flow rate of supply of the etching liquid (the suppliedamount per unit time), the concentration of the etching liquid, thetemperature of the etching liquid and the rotational speed of thesubstrate W. Hence, at least one of these conditions is changed, andthus it is possible to improve the flatness of the upper surface of thesubstrate W after the etching. Alternatively, the upper surface of thesubstrate W after the etching can be intentionally formed in the shapeof a cone or an inverted cone.

FIG. 8 is a block diagram showing the functional blocks of thecontroller 3.

In the following description, FIGS. 5 and 8 will be referenced. Aninformation acquisition portion 91, a setting dissolved oxygenconcentration determination portion 92, a setting atmosphere oxygenconcentration determination portion 93, a dissolved oxygen concentrationchange portion 94, an atmosphere oxygen concentration change portion 95and a processing execution portion 96 are functional blocks which arerealized by the execution of the program P installed in the controller 3by the CPU 82. In the following description, a case where the conditionsother than the dissolved oxygen concentration of the etching liquid andthe oxygen concentration in the atmosphere are constant and where atleast one of the dissolved oxygen concentration of the etching liquidand the oxygen concentration in the atmosphere is changed such that thedistribution of the amount of etching on the substrate W is changed willbe described.

As shown in FIG. 8, the controller 3 includes the informationacquisition portion 91 which acquires information input to the substrateprocessing apparatus 1. The information acquired by the informationacquisition portion 91 may be information that is input to the substrateprocessing apparatus 1 from the external device such as the hostcomputer or may be information that is input to the substrate processingapparatus 1 via the input device 88 by the operator.

The information input to the information acquisition portion 91 includesa setting central etching amount which indicates the setting value ofthe amount of etching in the central portion of the upper surface of thesubstrate W and a setting outer circumference etching amount whichindicates the setting value of the amount of etching in the outercircumferential portion of the upper surface of the substrate W. Whenthe entire region of the upper surface of the substrate W is uniformlyetched, instead of or in addition to the setting central etching amountand the setting outer circumference etching amount, the setting value ofthe amount of etching and the setting value of the uniformity of etchingmay be input to the information acquisition portion 91. The uniformityof etching is a value obtained by dividing a standard deviation by anaverage value. These pieces of information correspond to a requiredetching amount which indicates a required value of the amount of etchingin the upper surface of the substrate W.

The controller 3 includes the setting dissolved oxygen concentrationdetermination portion 92 which determines a setting dissolved oxygenconcentration that indicates the setting value of the dissolved oxygenconcentration of the etching liquid and the setting atmosphere oxygenconcentration determination portion 93 which determines a settingatmosphere oxygen concentration that indicates the setting value of theoxygen concentration in the atmosphere. The setting dissolved oxygenconcentration determination portion 92 stores dissolved oxygenconcentration determination data which indicates a relationship betweenthe etching rate in a landing position and the setting dissolved oxygenconcentration. The setting atmosphere oxygen concentration determinationportion 93 stores atmosphere oxygen concentration determination datawhich indicates a relationship between the gradient of the etching rateand a setting atmosphere oxygen concentration. The gradient of theetching rate means the gradient of a straight line which connects theetching rate in the landing position and an etching rate in an arbitraryposition within the upper surface of the substrate W.

The dissolved oxygen concentration determination data is produced basedon the measurement value of the etching rate in the landing positionwhen the setting dissolved oxygen concentration is changed to aplurality of values without the conditions other than the settingdissolved oxygen concentration being changed. The dissolved oxygenconcentration determination data may be a formula or a table whichindicates a relationship between the etching rate in the landingposition and the dissolved oxygen concentration or may be a form otherthan these. Similarly, the atmosphere oxygen concentration determinationdata is produced based on the measurement value of the gradient of theetching rate when the setting atmosphere oxygen concentration is changedto a plurality of values without the conditions other than the settingatmosphere oxygen concentration being changed. The atmosphere oxygenconcentration determination data may be a formula or a table whichindicates a relationship between the gradient of the etching rate andthe setting atmosphere oxygen concentration or may be a form other thanthese.

When the conditions other than the dissolved oxygen concentration of theetching liquid and the oxygen concentration in the atmosphere areconstant, the etching rate in the landing position mainly depends on thedissolved oxygen concentration of the etching liquid. In other words,when the dissolved oxygen concentration of the etching liquid is thesame, even if the oxygen concentration in the atmosphere is changed, theetching rate in the landing position is not changed or is hardlychanged. On the other hand, the gradient of the etching rate depends notonly on the oxygen concentration in the atmosphere but also on thedissolved oxygen concentration of the etching liquid. In other words,even when the oxygen concentration in the atmosphere is the same, if thedissolved oxygen concentration of the etching liquid is changed, thegradient of the etching liquid can be changed.

When the conditions other than the dissolved oxygen concentration of theetching liquid and the oxygen concentration in the atmosphere areconstant, if the etching rate in the landing position, the gradient ofthe etching rate, the time of supply of the etching liquid and thediameter of the substrate W are found, the estimation values of theamounts of etching in arbitrary positions within the upper surface ofthe substrate W including the central portion and the outercircumferential portions are found. In other words, when these arefound, the estimation values of the distribution of the amount ofetching within the upper surface of the substrate W including theestimation value of the amount of etching in the central portion of theupper surface of the substrate W and the estimation value of the amountof etching in the outer circumferential portion of the upper surface ofthe substrate W are found.

The setting dissolved oxygen concentration determination portion 92 usesthe dissolved oxygen concentration determination data to calculate orsearch for the value of the setting dissolved oxygen concentration inwhich the estimation value of the amount of etching in the centralportion of the upper surface of the substrate W corresponding to thelanding position is equal to or substantially equal to the settingcentral etching amount, and determines, as the setting dissolved oxygenconcentration, the value which is calculated or searched for. Similarly,the setting atmosphere oxygen concentration determination portion 93uses the atmosphere oxygen concentration determination data to calculateor search for the value of the setting atmosphere oxygen concentrationin which the estimation value of the amount of etching in the outercircumferential portion of the upper surface of the substrate W is equalto or substantially equal to the setting outer circumference etchingamount, and determines, as the setting atmosphere oxygen concentration,the value which is calculated or searched for.

When the etching liquid is the TMAH and the target to be etched is thepolysilicon film, the range of values which can be set as the settingdissolved oxygen concentration is, for example, 0.02 to 6.6 ppm (in acase where the processing is performed at 40° C.), and the range ofvalues which can be set as the setting atmosphere oxygen concentrationis, for example, 10 to 140000 ppm. The determined setting dissolvedoxygen concentration may be the minimum value in the range of valuesdescribed above or a value larger than the minimum value. The sameapplies to the determined setting atmosphere oxygen concentration.Although both the setting dissolved oxygen concentration and the settingatmosphere oxygen concentration can be the minimum values as a result,the setting dissolved oxygen concentration and the setting atmosphereoxygen concentration are determined based on the required etchingamount.

The controller 3 includes the dissolved oxygen concentration changeportion 94 which causes the dissolved oxygen concentration change unit67 to change an actual dissolved oxygen concentration of the etchingliquid such that the actual dissolved oxygen concentration of theetching liquid is equal or approached to the setting dissolved oxygenconcentration determined by the setting dissolved oxygen concentrationdetermination portion 92 and the atmosphere oxygen concentration changeportion 95 causes an atmosphere oxygen concentration change unit 97 tochange an actual oxygen concentration in the atmosphere such that theactual oxygen concentration in the atmosphere is equal or approached tothe setting atmosphere oxygen concentration determined by the settingatmosphere oxygen concentration determination portion 93. The atmosphereoxygen concentration change unit 97 includes the lower gas valve 21, thelower gas flow rate adjusting valve 22, the upper gas valve 57 and theupper gas flow rate adjusting valve 58 (see FIGS. 2 and 3).

The dissolved oxygen concentration change portion 94 may change thedissolved oxygen concentration of the etching liquid which is specifiedin the recipe or may cause, before the recipe is executed, the dissolvedoxygen concentration change unit 67 to change the actual dissolvedoxygen concentration of the etching liquid. Similarly, the atmosphereoxygen concentration change portion 95 may change the oxygenconcentration in the atmosphere which is specified in the recipe or maycause, before the recipe is executed, the atmosphere oxygenconcentration change unit 97 to change the actual oxygen concentrationin the atmosphere. When the recipe is changed, the recipe is executed soas to change the actual dissolved oxygen concentration or the actualatmosphere oxygen concentration.

The setting dissolved oxygen concentration and the setting atmosphereoxygen concentration may be changed for each of the substrates W, may bechanged every plurality of substrates W or may be changed per giventime. In other words, the same setting dissolved oxygen concentrationand the same setting atmosphere oxygen concentration may be applied to aplurality of substrates W. In this case, the setting dissolved oxygenconcentration and the setting atmosphere oxygen concentration may bechanged for each of the lots of the substrates W or may be changed eachtime the processing conditions for the substrate W performed by a deviceother than the substrate processing apparatus 1 are changed.

The controller 3 includes the processing execution portion 96 whichcontrols the substrate processing apparatus 1 so as to cause thesubstrate processing apparatus 1 to process the substrate W according tothe recipe. When the change of the setting dissolved oxygenconcentration and the setting atmosphere oxygen concentration iscompleted, the dissolved oxygen concentration change portion 94 and theatmosphere oxygen concentration change portion 95 notify the processingexecution portion 96 of the completion of the change. Thereafter, theprocessing execution portion 96 causes the processing unit 2, etc., toexecute the example of the processing shown in FIG. 6. Thus, in a statewhere the actual dissolved oxygen concentration of the etching liquid issubstantially equal to the determined setting dissolved oxygenconcentration and where the actual oxygen concentration in theatmosphere is substantially equal to the determined setting atmosphereoxygen concentration, the etching liquid is supplied to the uppersurface of the substrate W.

As described above, in the first preferred embodiment, the etchingliquid such as the TMAH having a low dissolved oxygen concentration issupplied to the upper surface of the substrate Win the state where theoxygen concentration in the atmosphere is lowered. Thus, it is possibleto supply the etching liquid to the entire region of the upper surfaceof the substrate W while controlling the amount of oxygen dissolved intothe etching liquid held on the substrate W. The actual dissolved oxygenconcentration of the etching liquid supplied to the upper surface of thesubstrate W is equal or approached to the setting dissolved oxygenconcentration. Similarly, the actual oxygen concentration in theatmosphere in contact with the etching liquid held on the upper surfaceof the substrate W is equal or approached to the setting atmosphereoxygen concentration.

The setting dissolved oxygen concentration and the setting atmosphereoxygen concentration are not set independently based on the requiredetching amount but are related to each other. Specifically, one of thesetting dissolved oxygen concentration and the setting atmosphere oxygenconcentration is determined based on the required etching amount. Then,based on the determined value (one of the setting dissolved oxygenconcentration and the setting atmosphere oxygen concentration) and therequired etching amount, the other of the setting dissolved oxygenconcentration and the setting atmosphere oxygen concentration isdetermined. In other words, not only the setting dissolved oxygenconcentration and the setting atmosphere oxygen concentration but alsothe difference between the setting dissolved oxygen concentration andthe setting atmosphere oxygen concentration is controlled.

As described above, the setting dissolved oxygen concentration and thesetting atmosphere oxygen concentration are lowered while controllingthe difference between the setting dissolved oxygen concentration andthe setting atmosphere oxygen concentration, and thus it is possible tochange the distribution of the amount of etching over the upper surfaceof the substrate W without changing the landing position of the etchingliquid with respect to the upper surface of the substrate W. Forexample, it is possible to uniformly etch the entire region of the uppersurface of the substrate W with a constant amount of etching, and toetch the upper surface of the substrate W such that the distribution ofthe amount of etching over the upper surface of the substrate W isformed in the shape of a cone or an inverted cone. Thus, it is possibleto etch the upper surface of the substrate W while controlling thedistribution of the amount of etching.

In the first preferred embodiment, a value which is larger than theminimum value in the range of values that can be set as the settingdissolved oxygen concentration or the setting atmosphere oxygenconcentration is set as the setting dissolved oxygen concentration orthe setting atmosphere oxygen concentration. In other words, unlike theconventional method in which the setting dissolved oxygen concentrationand the setting atmosphere oxygen concentration are set to values assmall as possible, the setting dissolved oxygen concentration, thesetting atmosphere oxygen concentration and the difference therebetweenare controlled. Thus, it is possible to etch the upper surface of thesubstrate W while controlling the distribution of the amount of etching.

In the first preferred embodiment, the landing position of the etchingliquid is positioned in the central portion of the upper surface of thesubstrate W after the start of the discharge until the stop of thedischarge. In such a case as well, the difference between the settingdissolved oxygen concentration and the setting atmosphere oxygenconcentration is controlled, and thus it is possible to control thedistribution of the amount of etching. Hence, it is not necessary tomove the landing position of the etching liquid with respect to theupper surface of the substrate W or to provide a plurality of liquiddischarge ports which discharge the etching liquid toward the uppersurface of the substrate W in order to control the distribution of theamount of etching.

In the first preferred embodiment, the setting dissolved oxygenconcentration and the setting atmosphere oxygen concentration are setsuch that the distribution of the amount of etching over the uppersurface of the substrate W is formed in the shape of a cone or aninverted cone. When the upper surface of the substrate W before theetching is in the shape of a cone, the upper surface of the substrate Wis etched such that the distribution of the amount of etching over theupper surface of the substrate W is formed in the shape of a cone, andthus it is possible to improve the flatness of the upper surface of thesubstrate W after the etching. Similarly, when the upper surface of thesubstrate W before the etching is in the shape of an inverted cone, theupper surface of the substrate W is etched such that the distribution ofthe amount of etching over the upper surface of the substrate W isformed in the shape of an inverted cone, and thus it is possible toimprove the flatness of the upper surface of the substrate W after theetching.

In the first preferred embodiment, after the setting dissolved oxygenconcentration is determined, the setting atmosphere oxygen concentrationis determined. The etching rate in the landing position depends on thedissolved oxygen concentration of the etching liquid. In other words,the setting atmosphere oxygen concentration does not significantlyaffect the etching rate in the landing position. Instead, the gradientof the etching rate, that is, the gradient of a straight line whichconnects the etching rate in the landing position and the etching ratein an arbitrary position within the upper surface of the substrate Wdepends on the dissolved oxygen concentration of the etching liquid andthe oxygen concentration in the atmosphere. Hence, when the settingdissolved oxygen concentration is previously determined, the etchingrate in the landing position and the gradient of the etching rate can beset relatively easily.

By contrast, when the setting atmosphere oxygen concentration ispreviously determined, the conditions other than the setting dissolvedoxygen concentration and the setting atmosphere oxygen concentration mayneed to be changed. For example, when the setting atmosphere oxygenconcentration is previously determined, in order to obtain the intendedgradient of the etching rate, the setting dissolved oxygen concentrationis significantly restricted. When the intended etching rate cannot beobtained by the determined setting dissolved oxygen concentration,another condition such as the time of supply of the etching liquid, theconcentration thereof, etc., may need to be changed. Hence, the settingdissolved oxygen concentration is previously determined, and thus theetching rate in the landing position and the gradient of the etchingrate can be set relatively easily.

In the first preferred embodiment, the nitrogen gas as an example of alow oxygen gas which has an oxygen concentration lower than the oxygenconcentration in air flows out from the upper central opening 38provided in the lower surface 36L of the shielding member 33 as anexample of an opposed member and flows into the space between the uppersurface of the substrate W and the lower surface 36L of the shieldingmember 33. Thus, the space between the substrate W and the shieldingmember 33 is filled with the nitrogen gas, and thus the oxygenconcentration in the atmosphere is lowered. Hence, as compared with acase where the oxygen concentration is lowered in the entire internalspace of the chamber 4, the used amount of nitrogen gas can be reduced,and thus it is possible to change the oxygen concentration in a shortperiod of time.

In the first preferred embodiment, in the state where the oxygenconcentration in the atmosphere is lowered, the etching liquid having alow dissolved oxygen concentration is supplied to the upper surface ofthe substrate W to which the polysilicon film is exposed. Thus, it ispossible to etch the polysilicon film formed on the upper surface of thesubstrate W while controlling the amount of oxygen dissolved into theetching liquid held on the substrate W. The polysilicon film is anexample of a thin film which is affected by the dissolved oxygenconcentration of the etching liquid. Hence, not only the settingdissolved oxygen concentration and the setting atmosphere oxygenconcentration but also the difference therebetween is controlled, andthus it is possible to etch the polysilicon film while controlling thedistribution of the amount of etching.

Second Preferred Embodiment

A second preferred embodiment mainly differs from the first preferredembodiment in that the structure of the shielding member 33 is differentand that a plurality of outer openings 101 which discharge a gas areprovided in the lower surface 36L of the shielding member 33.

FIG. 9 is a schematic view showing a vertical cross section of ashielding member 33 according to the second preferred embodiment of thepresent invention. FIG. 10 is a schematic view showing the bottomsurface of the shielding member 33 according to the second preferredembodiment of the present invention. In FIG. 9 to FIG. 10, componentsequivalent to the above described components shown in FIG. 1 to FIG. 8are designated by the same reference characters as in FIG. 1, etc., anddescription thereof is omitted.

As shown in FIG. 9, the shielding member 33 is arranged above a spinchuck 10. The shielding member 33 is a disc portion 36 which has anoutside diameter larger than the diameter of the substrate W. In otherwords, the tubular portion 37 of the first preferred embodiment is notprovided in the shielding member 33 of the second preferred embodiment.The shielding member 33 is held by a horizontal posture. The center lineof the shielding member 33 is arranged on a rotation axis A1. Theoutside diameter of the lower surface 36L of the shielding member 33 islarger than that of the substrate W. The lower surface 36L of theshielding member 33 is parallel to the upper surface of the substrate Wand faces the upper surface of the substrate W.

As shown in FIG. 10, the lower surface 36L of the shielding member 33has a circular ring shaped configuration which surrounds the rotationaxis A1. The inner circumferential edge of the lower surface 36L of theshielding member 33 defines an upper central opening 38 which is open inthe central portion of the lower surface 36L of the shielding member 33.The inner circumferential surface of the shielding member 33 defines athrough hole which extends upward from the upper central opening 38. Acenter nozzle 45 is inserted into the through hole of the shieldingmember 33. When the shielding member 33 is viewed from below, the centernozzle 45 is arranged within the upper central opening 38 of theshielding member 33.

As shown in FIG. 9, a shielding member raising/lowering unit 31 iscoupled to the shielding member 33 via a support shaft 100 which extendsupward from the shielding member 33. The center nozzle 45 is coupled tothe shielding member raising/lowering unit 31. The shielding memberraising/lowering unit 31 vertically raises and lowers the shieldingmember 33 between an upper position (the position of the shieldingmember 33 indicated by solid lines in FIG. 9) and a lower position (theposition of the shielding member 33 indicated by alternate long and twoshort dashed lines in FIG. 9). The center nozzle 45 is vertically movedbetween the upper position and the lower position together with theshielding member 33.

The upper position of the shielding member 33 is a retraction positionin which the lower surface 36L of the shielding member 33 is separatedupward from the upper surface of the substrate W such that scan nozzles(see a first chemical liquid nozzle 106 and a second chemical liquidnozzle 107 in FIG. 11) can enter between the upper surface of thesubstrate W and the lower surface 36L of the shielding member 33. Thelower position of the shielding member 33 is a proximate position inwhich the lower surface 36L of the shielding member 33 is close to theupper surface of the substrate W such that the scan nozzles cannot enterbetween the upper surface of the substrate W and the lower surface 36Lof the shielding member 33. The shielding member raising/lowering unit31 positions the shielding member 33 in an arbitrary position from thelower position to the upper position.

A first chemical liquid piping 50, a second chemical liquid piping 52and an upper rinse liquid piping 54 are connected to the center nozzle45. An upper gas piping 56 is connected not to the center nozzle 45 butto an upper tubular path 39 defined between the inner circumferentialsurface of the shielding member 33 and the outer circumferential surfaceof the center nozzle 45. The nitrogen gas supplied from the upper gaspiping 56 to the upper tubular path 39 flows downward within the uppertubular path 39 while flowing in the circumferential direction withinthe upper tubular path 39. Then, the nitrogen gas flows downward fromthe upper central opening 38 which is open in the central portion of thelower surface 36L of the shielding member 33. When the shielding member33 is arranged in the lower position, the nitrogen gas flowing out fromthe upper central opening 38 flows outward in the space between theupper surface of the substrate W and the lower surface 36L of theshielding member 33. Thus, the space between the substrate W and theshielding member 33 is filled with the nitrogen gas.

The shielding member 33 includes the outer openings 101 which are openedin the lower surface 36L of the shielding member 33 and an internal path102 which guides the gas to the outer openings 101. The internal path102 is provided within the shielding member 33. The individual outeropenings 101 are extended downward from the internal path 102. The outeropenings 101 face the outer circumferential portion of the upper surfaceof the substrate W. The outer openings 101 may be extended vertically ina downward direction from the internal path 102 or may be extendedobliquely downward from the internal path 102. FIG. 9 shows an examplewhere the outer openings 101 are extended obliquely downward toward theperiphery of the substrate W.

As shown in FIG. 10, the outer openings 101 are arranged on a circlewhich has a center arranged on the rotation axis A1. The internal path102 surrounds the rotation axis A1. When the shielding member 33 isviewed from below, the internal path 102 overlaps the outer openings101. The internal path 102 surrounds the upper central opening 38 of theshielding member 33. Similarly, the outer openings 101 surround theupper central opening 38 of the shielding member 33.

As shown in FIG. 9, the substrate processing apparatus 1 includes anupper gas piping 103 which guides the gas via the internal path 102 tothe outer openings 101, an upper gas valve 104 which is interposed inthe upper gas piping 103 and an upper gas flow rate adjusting valve 105which changes the flow rate of the gas supplied from the upper gaspiping 103 to the center nozzle 45. The upper gas piping 103 isconnected to the internal path 102 of the shielding member 33.

When the upper gas valve 104 is opened, the nitrogen gas as an exampleof an inert gas is supplied from the upper gas piping 103 to theinternal path 102 at a flow rate corresponding to the degree of openingof the upper gas flow rate adjusting valve 105, and flows in thecircumferential direction within the internal path 102. The nitrogen gaswithin the internal path 102 is supplied to each of the outer openings101 and is discharged downward from the outer openings 101. Thus, thenitrogen gas is supplied to the space between the substrate W and theshielding member 33. The upper gas valve 104 and the upper gas flow rateadjusting valve 105 are included in the atmosphere oxygen concentrationchange unit 97 (see FIG. 8).

In the second preferred embodiment, in addition to the actions andeffects of the first preferred embodiment, the following actions andeffects can be obtained. Specifically, in the second preferredembodiment, the upper central opening 38 and the outer openings 101 areprovided in the lower surface 36L of the shielding member 33. The uppercentral opening 38 faces the central portion of the upper surface of thesubstrate W. The outer openings 101 are arranged outside the uppercentral opening 38. The nitrogen gas flowing out from the upper centralopening 38 flows outward in the space between the substrate W and theshielding member 33. Similarly, the nitrogen gas flowing out from theouter openings 101 flows outward in the space between the substrate Wand the shielding member 33. Hence, as compared with a case where theouter openings 101 are not provided, another gas is unlikely to flow inthe space between the substrate W and the shielding member 33. Thus, itis possible to more accurately control the oxygen concentration in thespace between the substrate W and the shielding member 33.

Third Preferred Embodiment

A third preferred embodiment mainly differs from the first preferredembodiment in that the shielding member 33 is omitted and that an inertgas is supplied by an FFU 5 into the chamber 4.

FIG. 11 is a schematic view of the interior of a processing unit 2according to the third preferred embodiment of the present inventionwhen the interior is viewed horizontally. FIG. 12 is a schematic view ofthe interior of the processing unit 2 according to the third preferredembodiment of the present invention when the interior is viewed fromabove. In FIG. 11 to FIG. 12, components equivalent to the abovedescribed components shown in FIG. 1 to FIG. 10 are designated by thesame reference characters as in FIG. 1, etc., and description thereof isomitted.

As shown in FIG. 11, the processing unit 2 includes a first chemicalliquid nozzle 106 which discharges a first chemical liquid downwardtoward the upper surface of the substrate W, a second chemical liquidnozzle 107 which discharges a second chemical liquid downward toward theupper surface of the substrate Wand a rinse liquid nozzle 108 whichdischarges a rinse liquid downward toward the upper surface of thesubstrate W. The first chemical liquid piping 50, the second chemicalliquid piping 52 and the upper rinse liquid piping 54 are respectivelyconnected to the first chemical liquid nozzle 106, the second chemicalliquid nozzle 107 and the rinse liquid nozzle 108.

The rinse liquid nozzle 108 is fixed to the partition wall 6 of achamber 4. The rinse liquid discharged from the rinse liquid dischargeport 108 p of the rinse liquid nozzle 108 reaches the central portion ofthe upper surface of the substrate W. The rinse liquid nozzle 108 may bea scan nozzle which moves the landing position with respect to the uppersurface of the substrate W. In other words, a nozzle movement unit whichmoves the rinse liquid nozzle 108 horizontally may be provided in theprocessing unit 2.

The first chemical liquid nozzle 106 and the second chemical liquidnozzle 107 are scan nozzles. As shown in FIG. 12, the processing unit 2includes a first nozzle movement unit 109 that moves the first chemicalliquid nozzle 106 horizontally between a processing position in whichthe chemical liquid discharged from the first chemical liquid dischargeport 106 p of the first chemical liquid nozzle 106 is supplied to theupper surface of the substrate W and a retraction position in which thefirst chemical liquid nozzle 106 is arranged around the substrate W inplan view. The processing unit 2 includes a second nozzle movement unit110 that moves the second chemical liquid nozzle 107 horizontallybetween a processing position in which the chemical liquid dischargedfrom the second chemical liquid discharge port 107 p of the secondchemical liquid nozzle 107 is supplied to the upper surface of thesubstrate W and a retraction position in which the second chemicalliquid nozzle 107 is arranged around the substrate W in plan view.

The first nozzle movement unit 109 may be a turning unit which moves thefirst chemical liquid nozzle 106 horizontally along an arc-shaped paththat passes through the central portion of the substrate W in plan viewor may be a slide unit which moves the first chemical liquid nozzle 106horizontally along a linear path that passes through the central portionof the substrate W in plan view. Similarly, the second nozzle movementunit 110 may be a turning unit or may be a slide unit. FIG. 12 shows anexample where the first nozzle movement unit 109 and the second nozzlemovement unit 110 are turning units.

An upper gas piping 56 which guides the nitrogen gas as an example ofthe inert gas is connected to the FFU 5. When an upper gas valve 57 isopened, the nitrogen gas is supplied from the upper gas piping 56 to theFFU 5 at a flow rate corresponding to the degree of opening of the uppergas flow rate adjusting valve 58, and is fed by the FFU 5 to an upperspace Su within the chamber 4. The nitrogen gas supplied to the upperspace Su hits a rectifying plate 8 so as to diffuse in the upper spaceSu and flows downward through a plurality of through holes provided inthe entire region of the rectifying plate 8.

Since the upper surface of the substrate W faces directly the lowersurface of the rectifying plate 8, the nitrogen gas flowing downwardfrom the rectifying plate 8 is moved to the upper surface of thesubstrate W without being interrupted by the shielding member 33 (seeFIG. 2). Thereafter, the nitrogen gas is sucked into a processing cup 23and is discharged via an exhaust duct 9 (see FIG. 2) from the chamber 4.Thus, the interior of the chamber 4 is filled with the nitrogen gas, andthus the oxygen concentration within the chamber 4 is lowered. Theoxygen concentration within the chamber 4 is changed according to thedegree of opening of the upper gas valve 57 and the upper gas flow rateadjusting valve 58.

When a first chemical liquid supply step (step S3 in FIG. 6) isperformed, the first nozzle movement unit 109 moves the first chemicalliquid nozzle 106 from a standby position to the processing position.Thereafter, the first chemical liquid valve 51 is opened so as to causethe first chemical liquid nozzle 106 to start the discharge of the firstchemical liquid. When the first chemical liquid nozzle 106 dischargesthe first chemical liquid, the first nozzle movement unit 109 may movethe first chemical liquid nozzle 106 such that the landing position ofthe first chemical liquid is moved along a path passing through thecentral portion of the upper surface of the substrate W within the uppersurface of the substrate W or may stop the first chemical liquid nozzle106 such that the landing position of the first chemical liquid ispositioned in the central portion of the upper surface of the substrateW.

In a second chemical liquid supply step (step S5 in FIG. 6), instead ofthe first chemical liquid nozzle 106, the first chemical liquid valve 51and the first nozzle movement unit 109, the second chemical liquidnozzle 107, the second chemical liquid valve 53 and the second nozzlemovement unit 110 are used. In a first rinse liquid supply step (step S4in FIG. 6) and a second rinse liquid supply step (step S6 in FIG. 6),the upper rinse liquid valve 55 is opened and closed so as to dischargethe rinse liquid from the rinse liquid nozzle 108 toward the centralportion of the upper surface of the substrate W.

In the third preferred embodiment, in addition to the actions andeffects of the first preferred embodiment, the following actions andeffects can be obtained. Specifically, in the third preferredembodiment, the nitrogen gas as an example of a low oxygen gas flowsfrom the upper end portion of the chamber 4 into the chamber 4. Thenitrogen gas flowing into the chamber 4 flows toward the lower endportion of the chamber 4 and is discharged from the lower end portion ofthe chamber 4 to the outside of the chamber 4. Thus, the interior of thechamber 4 is filled with the nitrogen gas, and thus the oxygenconcentration in the atmosphere is lowered. Hence, the oxygenconcentration in the atmosphere can be lowered without provision ofmembers such as the shielding member 33 arranged above the substrate W.Thus, it is possible to downsize the chamber 4.

Fourth Preferred Embodiment

A fourth preferred embodiment mainly differs from the first preferredembodiment in that a plurality of groups of chemical liquid producingunits 61 and dissolved oxygen concentration change units 67 whichcorrespond to the same processing unit 2 are provided. FIG. 13 shows anexample where two groups of the chemical liquid producing units 61 andthe dissolved oxygen concentration change units 67 are provided.

FIG. 13 shows a schematic view showing the chemical liquid producingunits 61 and the dissolved oxygen concentration change units 67according to the fourth preferred embodiment. In FIG. 13, componentsequivalent to the above described components shown in FIG. 1 to FIG. 12are designated by the same reference characters as in FIG. 1, etc., anddescription thereof is omitted.

In the following description, “first” may be added to the front of anarrangement positioned on the left side of FIG. 13, and “second” may beadded to the front of an arrangement positioned on the right side ofFIG. 13. For example, a tank 62 on the left side of FIG. 13 may bereferred to as a “first tank 62A,” and a tank 62 on the right side ofFIG. 13 may be referred to as a “second tank 62B.”

The chemical liquid producing unit 61 includes a relay piping 111 whichguides a chemical liquid within a circulation piping 63 to a secondchemical liquid piping 52 and relay valves 112 which are interposed inthe relay piping 111. In the case of an example shown in FIG. 13,instead of the two relay valves 112, a three-way valve may be used. Whenthe first relay valve 112A (the relay valve 112 on the left side) isopened, the chemical liquid within the first tank 62A (the tank 62 onthe left side) is supplied via the second chemical liquid piping 52 to acenter nozzle 45. When the second relay valve 112B (the relay valve 112on the right side) is opened, the chemical liquid within the second tank62B (the tank 62 on the right side) is supplied via the second chemicalliquid piping 52 to the center nozzle 45.

The chemical liquid within the first tank 62A and the chemical liquidwithin the second tank 62B have different dissolved oxygenconcentrations from each other. In other words, the dissolved oxygenconcentrations of the chemical liquids are adjusted as follows. When thesetting value of the dissolved oxygen concentration of the chemicalliquid supplied to the upper surface of the substrate W, that is, thesetting dissolved oxygen concentration is determined, the controller 3selects which one of the first tank 62A and the second tank 62B storesthe chemical liquid having the dissolved oxygen concentration close tothe setting dissolved oxygen concentration that is determined. Then, thecontroller 3 discharges, in a second chemical liquid supply step (stepS5 in FIG. 6), the chemical liquid within the selected tank to thecenter nozzle 45. For example, when the first tank 62A is selected, thefirst relay valve 112A and the second chemical liquid valve 53 areopened, and thus the chemical liquid within the first tank 62A isdischarged from the center nozzle 45 toward the upper surface of thesubstrate W.

In the fourth preferred embodiment, in addition to the actions andeffects of the first preferred embodiment, the following actions andeffects can be obtained. Specifically, the etching liquids havingdifferent dissolved oxygen concentrations from each other are stored inthe first tank 62A and the second tank 62B. The determined settingdissolved oxygen concentration is compared with a first dissolved oxygenconcentration which indicates the dissolved oxygen concentration of theetching liquid within the first tank 62A and a second dissolved oxygenconcentration which indicates the dissolved oxygen concentration of theetching liquid within the second tank 62B. When the dissolved oxygenconcentration of the etching liquid within the first tank 62A is equalor close to the determined setting dissolved oxygen concentration, theetching liquid within the first tank 62A is supplied to the uppersurface of the substrate W. On the other hand, when the dissolved oxygenconcentration of the etching liquid within the second tank 62B is equalor close to the determined setting dissolved oxygen concentration, theetching liquid within the second tank 62B is supplied to the uppersurface of the substrate W.

It is difficult to change immediately the dissolved oxygen concentrationof the etching liquid. Hence, when the dissolved oxygen concentration ofthe etching liquid within the same tank 62 is changed, a certain amountof time is needed. By contrast, when the etching liquids havingdifferent dissolved oxygen concentrations from each other are previouslystored in the first tank 62A and the second tank 62B, the dissolvedoxygen concentration of the etching liquid supplied to the upper surfaceof the substrate W can be changed immediately. Thus, it is possible toreduce the downtime (time during which the substrate W processing cannotbe executed) of the substrate processing apparatus 1, and thus it ispossible to reduce the amount of decrease in the throughput (the numberof substrates W processed per unit time) of the substrate processingapparatus 1.

Other Preferred Embodiments

The present invention is not restricted to the contents of the abovedescribed preferred embodiments and various modifications are possible.

For example, the etching liquid such as the TMAH may be supplied not tothe upper surface of the substrate W but to the lower surface of thesubstrate W. Alternatively, the etching liquid may be supplied to boththe upper surface and the lower surface of the substrate W. In thesecases, the lower surface nozzle 15 may be used to discharge the etchingliquid.

The controller 3 may cause a plurality of liquid discharge ports tosimultaneously discharge the processing liquid toward a plurality ofpositions away in the radial direction of the substrate W so as tosupply the processing liquid to the upper surface or the lower surfaceof the substrate W. In this case, at least one of the flow rate, thetemperature and the concentration of the chemical liquid which isdischarged may be changed for each of the liquid discharge ports.

Similarly, the controller 3 may cause a plurality of gas discharge portsto simultaneously discharge the gas toward a plurality of positions awayin the radial direction of the substrate W so as to supply the gas tothe upper surface or the lower surface of the substrate W. For example,a plurality of gas discharge ports including the lower central opening18 may be provided in the upper surface 12 u of the spin base 12.

The controller 3 may previously determine the setting atmosphere oxygenconcentration instead of previously determining the setting dissolvedoxygen concentration.

The substrate processing apparatus 1 is not restricted to an apparatusfor processing a disc-shaped substrate W, and may be an apparatus forprocessing a polygonal substrate W.

Two or more arrangements among all the arrangements described above maybe combined. Two or more steps among all the steps described above maybe combined.

The FFU 5 is an example of a fan unit. The spin chuck 10 is an exampleof a substrate holding unit. The spin base 12 is an example of anopposed member. The upper surface 12 u is an example of an opposedsurface. The lower surface nozzle 15 is an example of an etching liquidsupply unit. The lower tubular path 19 is an example of a low oxygen gassupply unit. The lower gas piping 20 is an example of the low oxygen gassupply unit. The lower gas valve 21 is an example of an atmosphereoxygen concentration change unit. The lower gas flow rate adjustingvalve 22 is an example of the atmosphere oxygen concentration changeunit. The shielding member is an example of an opposed member 33. Thelower surface 36L is an example of the opposed surface. The uppertubular path 39 is an example of the low oxygen gas supply unit. Thecenter nozzle 45 is an example of the etching liquid supply unit. Theupper gas piping 56 is an example of the low oxygen gas supply unit. Theupper gas valve 57 is an example of the atmosphere oxygen concentrationchange unit. The upper gas flow rate adjusting valve 58 is an example ofthe atmosphere oxygen concentration change unit. The dissolved oxygenconcentration change unit 67 is an example of a dissolved oxygenconcentration change unit. The atmosphere oxygen concentration changeunit 97 is an example of the atmosphere oxygen concentration changeunit. The upper gas piping 103 is an example of the low oxygen gassupply unit. The upper gas valve 104 is an example of the atmosphereoxygen concentration change unit. The upper gas flow rate adjustingvalve 105 is an example of the atmosphere oxygen concentration changeunit. The second chemical liquid nozzle 107 is an example of the etchingliquid supply unit.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. A substrate processing apparatus comprising: asubstrate holding unit which holds a substrate horizontally; an etchingliquid supply unit which supplies a main surface of the substrate heldby the substrate holding unit with an etching liquid whose dissolvedoxygen is reduced; a chamber which houses the substrate held by thesubstrate holding unit; a low oxygen gas supply unit which causes a lowoxygen gas having an oxygen concentration lower than an oxygenconcentration of air to flow into the chamber housing the substrate soas to adjust an oxygen concentration in an atmosphere in contact withthe etching liquid held on the main surface of the substrate; adissolved oxygen concentration change unit which changes a dissolvedoxygen concentration of the etching liquid to be supplied to thesubstrate from the etching liquid supply unit; an atmosphere oxygenconcentration change unit which changes the oxygen concentration in theatmosphere to be adjusted by the low oxygen gas supply unit; and acontroller, wherein the controller executes performing a first oxygenconcentration determination step of determining one of (a) a settingdissolved oxygen concentration which indicates a setting value of thedissolved oxygen concentration of the etching liquid and (b) a settingatmosphere oxygen concentration which indicates a setting value of theoxygen concentration in the atmosphere in contact with the etchingliquid held on the main surface of the substrate, based on a requiredetching amount which indicates a required value of an amount of etchingof the main surface of the substrate; performing a second oxygenconcentration determination step of determining the other of (a) thesetting dissolved oxygen concentration and (b) the setting atmosphereoxygen concentration based on the required etching amount and based onthe one of (a) the setting dissolved oxygen concentration and (b) thesetting atmosphere oxygen concentration determined in the first oxygenconcentration determination step; a low oxygen gas supply step ofcausing the low oxygen gas, whose oxygen concentration is lower than anoxygen concentration of air and equal or approached to the settingatmosphere oxygen concentration determined in the first oxygenconcentration determination step or the second oxygen concentrationdetermination step, to flow into the chamber that houses the substrate;and an etching step of etching the main surface of the substrate bysupplying an entire region of the main surface of the substrate heldhorizontally with the etching liquid whose dissolved oxygen is reducedsuch that the dissolved oxygen concentration of the etching liquid isequal or approached to the setting dissolved oxygen concentrationdetermined in the first oxygen concentration determination step or thesecond oxygen concentration determination step, while causing the lowoxygen gas that has flowed into the chamber in the low oxygen gas supplystep to be in contact with the etching liquid held on the main surfaceof the substrate.
 2. The substrate processing apparatus according toclaim 1, wherein one of the first oxygen concentration determinationstep and the second oxygen concentration determination step includeseither a step of determining, as the setting dissolved oxygenconcentration, a value larger than a minimum value in a range of valueswhich can be set as the setting dissolved oxygen concentration or a stepof determining, as the setting atmosphere oxygen concentration, a valuelarger than a minimum value in a range of values which can be set as thesetting atmosphere oxygen concentration.
 3. The substrate processingapparatus according to claim 1, wherein the etching liquid supply unitincludes a liquid discharge port which discharges the etching liquidtoward the main surface of the substrate held by the substrate holdingunit, and the etching step includes a liquid discharge step of causingthe liquid discharge port to discharge the etching liquid, whosedissolved oxygen is reduced such that the dissolved oxygen concentrationof the etching liquid is equal or approached to the setting dissolvedoxygen concentration determined in the first oxygen concentrationdetermination step or the second oxygen concentration determinationstep, toward the main surface of the substrate held horizontally, whilelocating a landing position of the etching liquid, where the etchingliquid discharged from the liquid discharge port first contacts the mainsurface of the substrate, in a central portion of the main surface ofthe substrate after start of the discharge of the etching liquid untilstop of the discharge of the etching liquid.
 4. The substrate processingapparatus according to claim 3, wherein the second oxygen concentrationdetermination step is a step of determining, based on the requiredetching amount and the one of the setting dissolved oxygen concentrationand the setting atmosphere oxygen concentration determined in the firstoxygen concentration determination step, the other of the settingdissolved oxygen concentration and the setting atmosphere oxygenconcentration such that a distribution of the amount of etching over themain surface of the substrate is formed in a shape of a cone or aninverted cone.
 5. The substrate processing apparatus according to claim1, wherein the first oxygen concentration determination step is a stepof determining the setting dissolved oxygen concentration based on therequired etching amount, and the second oxygen concentrationdetermination step is a step of determining the setting atmosphereoxygen concentration based on the required etching amount and thesetting dissolved oxygen concentration determined in the first oxygenconcentration determination step.
 6. The substrate processing apparatusaccording to claim 1, further comprising: an opposed member which ismovable within the chamber and which includes an opposed surface thatfaces the main surface of the substrate held by the substrate holdingunit and an opening provided in the opposed surface, wherein the lowoxygen gas supply step includes a step of causing the low oxygen gas toflow from the opening provided in the opposed surface to a space betweenthe main surface of the substrate and the opposed surface of the opposedmember, while causing the opposed surface of the opposed member which ismovable within the chamber to face the main surface of the substrate. 7.The substrate processing apparatus according to claim 6, wherein theopening of the opposed member includes a central opening that isprovided in the opposed surface of the opposed member and faces acentral portion of the main surface of the substrate and an outeropening that is provided in the opposed surface of the opposed memberand faces a portion of the main surface of the substrate other than thecentral portion of the main surface of the substrate, and the low oxygengas supply step includes a step of causing the low oxygen gas to flowfrom the central opening to the space between the main surface of thesubstrate and the opposed surface of the opposed member and a step ofcausing the low oxygen gas to flow from the outer opening to the spacebetween the main surface of the substrate and the opposed surface of theopposed member.
 8. The substrate processing apparatus according to claim1, wherein the low oxygen gas supply unit includes a fan unit whichcauses the low oxygen gas to flow from an upper end portion of thechamber into the chamber and an exhaust duct which causes a gas withinthe chamber to flow out from a lower end portion of the chamber, and thelow oxygen gas supply step includes a step of causing the low oxygen gasto flow from the upper end portion of the chamber into the chamber whilecausing the gas within the chamber to flow out from the lower endportion of the chamber.
 9. The substrate processing apparatus accordingto claim 1, wherein the etching liquid supply unit includes a first tankwhich stores the etching liquid, a second tank which stores the etchingliquid, a first dissolved oxygen concentration change unit which lowersthe dissolved oxygen concentration of the etching liquid within thefirst tank and a second dissolved oxygen concentration change unit whichlowers the dissolved oxygen concentration of the etching liquid withinthe second tank, the controller further executes a first dissolvedoxygen concentration adjustment step of lowering the dissolved oxygenconcentration of the etching liquid within the first tank to the firstdissolved oxygen concentration by reducing the dissolved oxygen in theetching liquid and a second dissolved oxygen concentration adjustmentstep of lowering the dissolved oxygen concentration of the etchingliquid within a second tank to the second dissolved oxygen concentrationdifferent from the first dissolved oxygen concentration by reducing thedissolved oxygen in the etching liquid and the etching step includes aselection step of selecting, among the first tank and the second tank, atank that stores the etching liquid having the dissolved oxygenconcentration closer to the setting dissolved oxygen concentrationdetermined in the first oxygen concentration determination step or thesecond oxygen concentration determination step and a liquid dischargestep of discharging the etching liquid within the tank selected in theselection step toward the main surface of the substrate heldhorizontally.
 10. The substrate processing apparatus according to claim1, wherein the etching step is a step of etching a polysilicon filmformed on the main surface of the substrate by supplying the entireregion of the main surface held horizontally with the etching liquidwhose dissolved oxygen is reduced such that the dissolved oxygenconcentration of the etching liquid is equal or approached to thesetting dissolved oxygen concentration determined in the first oxygenconcentration determination step or the second oxygen concentrationdetermination step while causing the low oxygen gas that has flowed intothe chamber in the low oxygen gas supply step to be in contact with theetching liquid held on the main surface of the substrate.